A026443 a(n) = least positive integer > a(n-1) and not a(i)*a(j)+2 for 1<=i<j<=n, with initial terms 1,2.

1, 2, 3, 6, 7, 10, 11, 15, 18, 19, 25, 26, 29, 30, 33, 34, 37, 41, 42, 45, 46, 49, 50, 53, 57, 58, 61, 64, 65, 69, 73, 74, 78, 81, 82, 85, 88, 91, 95, 96, 99, 103, 106, 109, 114, 115, 119, 120, 123, 126, 127, 131, 134, 138, 139, 142, 143

Offset

1,2

Links

Ivan Neretin, Table of n, a(n) for n = 1..1000

Mathematica

a = {1, 2}; used = {a[[1]]*a[[2]] + 2}; Do[k = a[[-1]] + 1;
 While[MemberQ[used, k], k++]; used = Union[used, k*a + 2];
AppendTo[a, k], {n, 3, 60}]; a (* Ivan Neretin, Mar 06 2016 *)

Crossrefs

Similar sequences with different starting conditions: A026444 (1,3), A026445 (2,3), A026446 (2,4), A026447 (3,4).

Related sequences with definition using any products (not necessarily distinct) and with various starting conditions: A026448 (1,2), A026449 (1,3), A026450 (2,3), A026451 (2,4), A026452 (3,4).

Sequence in context: A073170 A014689 A117206 * A345251 A349257 A204323

Adjacent sequences: A026440 A026441 A026442 * A026444 A026445 A026446

Keyword

nonn

Author

Clark Kimberling

Extensions

Name clarified by Robert C. Lyons, Feb 07 2025

Status

approved