A112992 Numbers k such that ceiling(2^(2^k mod k)/3) is odd.

1, 2, 4, 8, 16, 25, 32, 45, 55, 64, 91, 95, 99, 125, 128, 135, 143, 153, 155, 161, 175, 187, 225, 235, 245, 247, 256, 261, 273, 275, 279, 285, 289, 297, 319, 329, 333, 335, 355, 363, 369, 387, 391, 403, 407, 413, 423, 425, 429, 435, 437, 441, 459, 473, 477, 481, 483, 493

Offset

1,2

Comments

Conjecture: the odd values of ceiling(2^(2^k mod k)/3) are Jacobsthal numbers (and the even values are 1 plus a Jacobsthal number).

Links

Table of n, a(n) for n=1..58.

Mathematica

Select[Range[493], OddQ[Ceiling[2^PowerMod[2, #, #]/3]]&] (* James C. McMahon, Jun 14 2024 *)

Prog

(PARI) isok(k) = (ceil(2^lift(Mod(2, k)^k)/3) % 2) == 1; \\ Michel Marcus, Jun 14 2024

Crossrefs

Cf. A005578, A001045.

Sequence in context: A119311 A305183 A360642 * A202274 A070789 A302588

Adjacent sequences: A112989 A112990 A112991 * A112993 A112994 A112995

Keyword

easy,nonn

Author

Paul Barry, Oct 08 2005

Status

approved