| Step | Hyp | Ref | Expression | 
						
							| 1 |  | eqeq2 |  |-  ( x = 1 -> ( ( #b ` a ) = x <-> ( #b ` a ) = 1 ) ) | 
						
							| 2 |  | oveq2 |  |-  ( x = 1 -> ( 0 ..^ x ) = ( 0 ..^ 1 ) ) | 
						
							| 3 |  | fzo01 |  |-  ( 0 ..^ 1 ) = { 0 } | 
						
							| 4 | 2 3 | eqtrdi |  |-  ( x = 1 -> ( 0 ..^ x ) = { 0 } ) | 
						
							| 5 | 4 | sumeq1d |  |-  ( x = 1 -> sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) = sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) | 
						
							| 6 | 5 | eqeq2d |  |-  ( x = 1 -> ( a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) <-> a = sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) | 
						
							| 7 | 1 6 | imbi12d |  |-  ( x = 1 -> ( ( ( #b ` a ) = x -> a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) <-> ( ( #b ` a ) = 1 -> a = sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 8 | 7 | ralbidv |  |-  ( x = 1 -> ( A. a e. NN0 ( ( #b ` a ) = x -> a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) <-> A. a e. NN0 ( ( #b ` a ) = 1 -> a = sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 9 |  | eqeq2 |  |-  ( x = y -> ( ( #b ` a ) = x <-> ( #b ` a ) = y ) ) | 
						
							| 10 |  | oveq2 |  |-  ( x = y -> ( 0 ..^ x ) = ( 0 ..^ y ) ) | 
						
							| 11 | 10 | sumeq1d |  |-  ( x = y -> sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) = sum_ k e. ( 0 ..^ y ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) | 
						
							| 12 | 11 | eqeq2d |  |-  ( x = y -> ( a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) <-> a = sum_ k e. ( 0 ..^ y ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) | 
						
							| 13 | 9 12 | imbi12d |  |-  ( x = y -> ( ( ( #b ` a ) = x -> a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) <-> ( ( #b ` a ) = y -> a = sum_ k e. ( 0 ..^ y ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 14 | 13 | ralbidv |  |-  ( x = y -> ( A. a e. NN0 ( ( #b ` a ) = x -> a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) <-> A. a e. NN0 ( ( #b ` a ) = y -> a = sum_ k e. ( 0 ..^ y ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 15 |  | eqeq2 |  |-  ( x = ( y + 1 ) -> ( ( #b ` a ) = x <-> ( #b ` a ) = ( y + 1 ) ) ) | 
						
							| 16 |  | oveq2 |  |-  ( x = ( y + 1 ) -> ( 0 ..^ x ) = ( 0 ..^ ( y + 1 ) ) ) | 
						
							| 17 | 16 | sumeq1d |  |-  ( x = ( y + 1 ) -> sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) = sum_ k e. ( 0 ..^ ( y + 1 ) ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) | 
						
							| 18 | 17 | eqeq2d |  |-  ( x = ( y + 1 ) -> ( a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) <-> a = sum_ k e. ( 0 ..^ ( y + 1 ) ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) | 
						
							| 19 | 15 18 | imbi12d |  |-  ( x = ( y + 1 ) -> ( ( ( #b ` a ) = x -> a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) <-> ( ( #b ` a ) = ( y + 1 ) -> a = sum_ k e. ( 0 ..^ ( y + 1 ) ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 20 | 19 | ralbidv |  |-  ( x = ( y + 1 ) -> ( A. a e. NN0 ( ( #b ` a ) = x -> a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) <-> A. a e. NN0 ( ( #b ` a ) = ( y + 1 ) -> a = sum_ k e. ( 0 ..^ ( y + 1 ) ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 21 |  | eqeq2 |  |-  ( x = L -> ( ( #b ` a ) = x <-> ( #b ` a ) = L ) ) | 
						
							| 22 |  | oveq2 |  |-  ( x = L -> ( 0 ..^ x ) = ( 0 ..^ L ) ) | 
						
							| 23 | 22 | sumeq1d |  |-  ( x = L -> sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) = sum_ k e. ( 0 ..^ L ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) | 
						
							| 24 | 23 | eqeq2d |  |-  ( x = L -> ( a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) <-> a = sum_ k e. ( 0 ..^ L ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) | 
						
							| 25 | 21 24 | imbi12d |  |-  ( x = L -> ( ( ( #b ` a ) = x -> a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) <-> ( ( #b ` a ) = L -> a = sum_ k e. ( 0 ..^ L ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 26 | 25 | ralbidv |  |-  ( x = L -> ( A. a e. NN0 ( ( #b ` a ) = x -> a = sum_ k e. ( 0 ..^ x ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) <-> A. a e. NN0 ( ( #b ` a ) = L -> a = sum_ k e. ( 0 ..^ L ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 27 |  | 0cnd |  |-  ( a e. NN0 -> 0 e. CC ) | 
						
							| 28 |  | 2nn |  |-  2 e. NN | 
						
							| 29 | 28 | a1i |  |-  ( a e. NN0 -> 2 e. NN ) | 
						
							| 30 |  | 0zd |  |-  ( a e. NN0 -> 0 e. ZZ ) | 
						
							| 31 |  | nn0rp0 |  |-  ( a e. NN0 -> a e. ( 0 [,) +oo ) ) | 
						
							| 32 |  | digvalnn0 |  |-  ( ( 2 e. NN /\ 0 e. ZZ /\ a e. ( 0 [,) +oo ) ) -> ( 0 ( digit ` 2 ) a ) e. NN0 ) | 
						
							| 33 | 29 30 31 32 | syl3anc |  |-  ( a e. NN0 -> ( 0 ( digit ` 2 ) a ) e. NN0 ) | 
						
							| 34 | 33 | nn0cnd |  |-  ( a e. NN0 -> ( 0 ( digit ` 2 ) a ) e. CC ) | 
						
							| 35 |  | 1cnd |  |-  ( a e. NN0 -> 1 e. CC ) | 
						
							| 36 | 34 35 | mulcld |  |-  ( a e. NN0 -> ( ( 0 ( digit ` 2 ) a ) x. 1 ) e. CC ) | 
						
							| 37 | 27 36 | jca |  |-  ( a e. NN0 -> ( 0 e. CC /\ ( ( 0 ( digit ` 2 ) a ) x. 1 ) e. CC ) ) | 
						
							| 38 | 37 | adantr |  |-  ( ( a e. NN0 /\ ( #b ` a ) = 1 ) -> ( 0 e. CC /\ ( ( 0 ( digit ` 2 ) a ) x. 1 ) e. CC ) ) | 
						
							| 39 |  | oveq1 |  |-  ( k = 0 -> ( k ( digit ` 2 ) a ) = ( 0 ( digit ` 2 ) a ) ) | 
						
							| 40 |  | oveq2 |  |-  ( k = 0 -> ( 2 ^ k ) = ( 2 ^ 0 ) ) | 
						
							| 41 |  | 2cn |  |-  2 e. CC | 
						
							| 42 |  | exp0 |  |-  ( 2 e. CC -> ( 2 ^ 0 ) = 1 ) | 
						
							| 43 | 41 42 | ax-mp |  |-  ( 2 ^ 0 ) = 1 | 
						
							| 44 | 40 43 | eqtrdi |  |-  ( k = 0 -> ( 2 ^ k ) = 1 ) | 
						
							| 45 | 39 44 | oveq12d |  |-  ( k = 0 -> ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) = ( ( 0 ( digit ` 2 ) a ) x. 1 ) ) | 
						
							| 46 | 45 | sumsn |  |-  ( ( 0 e. CC /\ ( ( 0 ( digit ` 2 ) a ) x. 1 ) e. CC ) -> sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) = ( ( 0 ( digit ` 2 ) a ) x. 1 ) ) | 
						
							| 47 | 38 46 | syl |  |-  ( ( a e. NN0 /\ ( #b ` a ) = 1 ) -> sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) = ( ( 0 ( digit ` 2 ) a ) x. 1 ) ) | 
						
							| 48 | 34 | adantr |  |-  ( ( a e. NN0 /\ ( #b ` a ) = 1 ) -> ( 0 ( digit ` 2 ) a ) e. CC ) | 
						
							| 49 | 48 | mulridd |  |-  ( ( a e. NN0 /\ ( #b ` a ) = 1 ) -> ( ( 0 ( digit ` 2 ) a ) x. 1 ) = ( 0 ( digit ` 2 ) a ) ) | 
						
							| 50 |  | blen1b |  |-  ( a e. NN0 -> ( ( #b ` a ) = 1 <-> ( a = 0 \/ a = 1 ) ) ) | 
						
							| 51 | 50 | biimpa |  |-  ( ( a e. NN0 /\ ( #b ` a ) = 1 ) -> ( a = 0 \/ a = 1 ) ) | 
						
							| 52 |  | vex |  |-  a e. _V | 
						
							| 53 | 52 | elpr |  |-  ( a e. { 0 , 1 } <-> ( a = 0 \/ a = 1 ) ) | 
						
							| 54 | 51 53 | sylibr |  |-  ( ( a e. NN0 /\ ( #b ` a ) = 1 ) -> a e. { 0 , 1 } ) | 
						
							| 55 |  | 0dig2pr01 |  |-  ( a e. { 0 , 1 } -> ( 0 ( digit ` 2 ) a ) = a ) | 
						
							| 56 | 54 55 | syl |  |-  ( ( a e. NN0 /\ ( #b ` a ) = 1 ) -> ( 0 ( digit ` 2 ) a ) = a ) | 
						
							| 57 | 47 49 56 | 3eqtrrd |  |-  ( ( a e. NN0 /\ ( #b ` a ) = 1 ) -> a = sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) | 
						
							| 58 | 57 | ex |  |-  ( a e. NN0 -> ( ( #b ` a ) = 1 -> a = sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) | 
						
							| 59 | 58 | rgen |  |-  A. a e. NN0 ( ( #b ` a ) = 1 -> a = sum_ k e. { 0 } ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) | 
						
							| 60 |  | nn0sumshdiglem1 |  |-  ( y e. NN -> ( A. a e. NN0 ( ( #b ` a ) = y -> a = sum_ k e. ( 0 ..^ y ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) -> A. a e. NN0 ( ( #b ` a ) = ( y + 1 ) -> a = sum_ k e. ( 0 ..^ ( y + 1 ) ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) ) | 
						
							| 61 | 8 14 20 26 59 60 | nnind |  |-  ( L e. NN -> A. a e. NN0 ( ( #b ` a ) = L -> a = sum_ k e. ( 0 ..^ L ) ( ( k ( digit ` 2 ) a ) x. ( 2 ^ k ) ) ) ) |