A063429 Smallest k such that 2^k has exactly n 3's in its decimal representation.

1, 5, 49, 25, 35, 109, 96, 128, 135, 169, 182, 156, 208, 302, 310, 277, 221, 300, 346, 498, 387, 502, 563, 507, 503, 611, 550, 585, 615, 681, 731, 817, 819, 835, 779, 860, 849, 840, 879, 997, 1016, 925, 1066, 1161, 1117, 1186, 1282, 1090, 1293, 1251, 1444

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], 3] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
With[{dr=Table[{k, DigitCount[2^k, 10, 3]}, {k, 1500}]}, Table[SelectFirst[dr, #[[2]]==n&], {n, 0, 50}]][[;; , 1]] (* Harvey P. Dale, Jul 30 2023 *)

Prog

(PARI) a(n)={my(k=1); while(n<>#select(d->d==3, digits(2^k)), k++); k} \\ Harry J. Smith, Aug 20 2009, Andrew Howroyd, Jun 26 2018

Crossrefs

Cf. A063115, A063426, A063430, A063526, A063540, A063552, A063553, A063554.

Sequence in context: A346183 A224510 A333982 * A297856 A298091 A298053

Adjacent sequences: A063426 A063427 A063428 * A063430 A063431 A063432

Keyword

base,nonn

Author

Robert G. Wilson v, Aug 10 2001

Extensions

Name corrected by Jon E. Schoenfield, Jun 25 2018

Status

approved