A063430 Smallest k such that 2^k has exactly n 4's in its decimal representation.

1, 2, 18, 22, 64, 91, 117, 111, 164, 138, 182, 233, 219, 253, 343, 266, 264, 321, 315, 331, 450, 349, 451, 469, 553, 504, 510, 687, 592, 630, 710, 744, 808, 767, 828, 889, 722, 951, 789, 942, 918, 964, 1066, 1033, 890, 1183, 1263, 1171, 1229, 1130, 1291

Offset

0,2

Links

Harry J. Smith, Table of n, a(n) for n = 0..150

Mathematica

a = {}; Do[k = 1; While[ Count[ IntegerDigits[2^k], 4] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a

Prog

(PARI) a(n)={my(k=1); while(n<>#select(d->d==4, digits(2^k)), k++); k} \\ Harry J. Smith, Aug 20 2009, Andrew Howroyd, Jun 26 2018

Crossrefs

Cf. A063115, A063426, A063429, A063526, A063540, A063552, A063553, A063554.

Sequence in context: A247457 A015787 A322489 * A031104 A115042 A191461

Adjacent sequences: A063427 A063428 A063429 * A063431 A063432 A063433

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 10 2001

Extensions

Name corrected by Jon E. Schoenfield, Jun 25 2018

Status

approved