A039420 Numbers whose base-10 representation has the same nonzero number of 3's and 7's.

37, 73, 137, 173, 237, 273, 307, 317, 327, 347, 357, 367, 370, 371, 372, 374, 375, 376, 378, 379, 387, 397, 437, 473, 537, 573, 637, 673, 703, 713, 723, 730, 731, 732, 734, 735, 736, 738, 739, 743, 753, 763, 783, 793, 837, 873, 937, 973, 1037, 1073

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

filter:= proc(n) local L;
  L:= convert(n, base, 10);
  has(L, 3) and numboccur(3, L) = numboccur(7, L)
end proc:
select(filter, [$1..5000]); # Robert Israel, Sep 24 2019

Crossrefs

Sequence in context: A093838 A055604 A135952 * A043243 A044023 A179579

Adjacent sequences: A039417 A039418 A039419 * A039421 A039422 A039423

Keyword

nonn,base,easy

Author

Olivier Gérard

Status

approved