A272766 Numbers n such that A281363(n) = n-1.

2, 3, 4, 6, 7, 10, 15, 19, 22, 30, 31, 34, 36, 51, 52, 54, 70, 75, 90, 91, 96, 99, 100, 106, 114, 115, 120, 135, 136, 156, 174, 190, 199, 210, 231, 244, 271, 286, 300, 316, 330, 346, 351, 370, 376, 394, 411, 414, 415, 430, 439, 496, 510, 516, 520, 531, 546, 559, 576, 615

Offset

1,1

Comments

Conjecture: primorial numbers (A002110) are terms of this sequence.

Links

Table of n, a(n) for n=1..60.

Mathematica

Table[SelectFirst[Range[10^5], PowerMod[2^#, 2 n, 4 n^2 - 1] == 1 &] /. k_ /; k != n - 1 -> Nothing, {n, 620}] + 1 (* Version 10.2, or *)
Rest@ Union@ Table[If[# == n - 1, #, 0] &@ Block[{m = 1}, While[PowerMod[2^m, 2 n, 4 n^2 - 1] != 1, m++]; m], {n, 620}] + 1 (* Michael De Vlieger, May 06 2016, after Giovanni Resta at A281363 *)

Crossrefs

Cf. A002110, A281363.

Sequence in context: A355393 A163771 A194855 * A271340 A362851 A117851

Adjacent sequences: A272763 A272764 A272765 * A272767 A272768 A272769

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, May 06 2016

Status

approved