A162600 a(n) = the smallest integer > n that has yet to occur in the sequence, and that is not coprime to n.

4, 6, 8, 10, 9, 14, 12, 15, 16, 22, 18, 26, 20, 21, 24, 34, 27, 38, 25, 28, 30, 46, 32, 35, 36, 33, 40, 58, 39, 62, 42, 44, 48, 45, 50, 74, 52, 51, 54, 82, 49, 86, 55, 57, 56, 94, 60, 63, 64, 66, 65, 106, 68, 70, 72, 69, 76, 118, 75, 122, 78, 77, 80, 85, 81, 134, 84, 87, 88, 142

Offset

2,1

Comments

Is this a permutation of the composite integers?

Links

Table of n, a(n) for n=2..71.

Mathematica

g[n_] := g[n] = Block[{k = n + 1, t = Table[ g@i, {i, 2, n - 1}]}, While[ MemberQ[t, k] || GCD[n, k] == 1, k++ ]; k]; Table[ g@n, {n, 2, 71}] (* or *) f[lst_] := Block[{len = 2 + Length@lst}, k = 1 + len; While[ MemberQ[lst, k] || GCD[len, k] == 1, k++ ]; Append[lst, k]]; Nest[f, {}, 70] (* Robert G. Wilson v, Aug 17 2009 *)

Crossrefs

Sequence in context: A331208 A362818 A191488 * A071537 A161396 A145256

Adjacent sequences: A162597 A162598 A162599 * A162601 A162602 A162603

Keyword

nonn

Author

Leroy Quet, Jul 07 2009

Extensions

a(17) and further terms from Robert G. Wilson v, Aug 17 2009

Status

approved