A361461 - OEIS

A361461

Numbers k such that x(k+1) = 2 * x(k), when x(1)=1 and x(n) = x(n-1) + lcm(x(n-1),n), i.e., x(n) = A135504(n).

%I #17 Mar 14 2023 18:31:47

%S 2,5,7,8,11,13,15,17,19,20,23,26,27,29,31,34,35,37,39,41,43,44,47,48,

%T 49,53,54,55,56,59,61,62,63,65,67,69,71,73,74,75,76,79,80,83,84,87,89,

%U 92,94,95,97,98,99,101,103,104,107,109,110,111,113,116,118,119,120,123,124,125,127,129,131,132

%N Numbers k such that x(k+1) = 2 * x(k), when x(1)=1 and x(n) = x(n-1) + lcm(x(n-1),n), i.e., x(n) = A135504(n).

%C Numbers k such that A135504(k) is a multiple of k+1.

%C It is conjectured that this sequence gives also all numbers k for which A135506(k) is not a prime. See Ruiz-Cabello paper.

%H Serafín Ruiz-Cabello, <a href="http://arxiv.org/abs/1504.05041">On the use of the lowest common multiple to build a prime-generating recurrence</a>, arXiv:1504.05041 [math.CO], 2015.

%o (PARI) isA361461(n) = A361460(n);

%Y Positions of 1's in A135506.

%Y Cf. A135504, A361460 (characteristic function), A361464.

%K nonn

%O 1,1

%A _Antti Karttunen_, Mar 13 2023