A338062 Numbers k such that the Enots Wolley sequence A336957(k) is odd.

1, 4, 5, 8, 9, 12, 13, 16, 17, 20, 21, 24, 25, 28, 29, 32, 33, 36, 37, 40, 41, 44, 45, 48, 49, 52, 53, 56, 57, 60, 61, 64, 65, 68, 69, 72, 73, 76, 77, 80, 81, 84, 85, 88, 89, 92, 93, 96, 97, 100, 101, 104, 105, 108, 109, 112, 113, 116, 117, 120, 121, 124, 125, 128, 129, 132, 133, 136, 137

Offset: 1

Author

N. J. A. Sloane, Oct 18 2020

Keywords

• nonn

Comments

a(n) = A042948(n) for n<=1065, but then the two sequences start to differ. - R. J. Mathar, Nov 06 2020

Links

• N. J. A. Sloane, Table of n, a(n) for n = 1..20000

Crossrefs

Cf. A336957, A338063-A338069.

Programs

Mathematica

M = 1000;
A[1] = 1; A[2] = 2;
Clear[B]; B[_] = 0;
For[n = 3, True, n++, For[k = 3, k <= M, k++, If[B[k] == 0 && GCD[k, A[n-1]] > 1 && GCD[k, A[n-2]] == 1, If[Length[FactorInteger[k][[All, 1]] ~Complement~ FactorInteger[A[n-1]][[All, 1]]] > 0, A[n] = k; B[k] = 1; Break[]]]]; If[k > M, Break[]]];
Reap[For[k = 1, k <= M, k++, If[OddQ[A[k]], Sow[k]]]][[2, 1]] (* Jean-François Alcover, Oct 23 2020, after Maple code in A336957 *)