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).

2, 5, 7, 8, 11, 13, 15, 17, 19, 20, 23, 26, 27, 29, 31, 34, 35, 37, 39, 41, 43, 44, 47, 48, 49, 53, 54, 55, 56, 59, 61, 62, 63, 65, 67, 69, 71, 73, 74, 75, 76, 79, 80, 83, 84, 87, 89, 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

Offset

1,1

Comments

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

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

Links

Table of n, a(n) for n=1..72.

Serafín Ruiz-Cabello, On the use of the lowest common multiple to build a prime-generating recurrence, arXiv:1504.05041 [math.CO], 2015.

Prog

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

Crossrefs

Positions of 1's in A135506.

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

Sequence in context: A277266 A047268 A039580 * A189296 A051279 A288464

Adjacent sequences: A361458 A361459 A361460 * A361462 A361463 A361464

Keyword

nonn

Author

Antti Karttunen, Mar 13 2023

Status

approved