A026437 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2.

1, 2, 4, 5, 6, 8, 10, 12, 13, 14, 16, 17, 18, 20, 21, 22, 26, 28, 30, 32, 34, 36, 37, 38, 40, 42, 44, 45, 46, 48, 50, 52, 53, 54, 56, 57, 58, 60, 61, 62, 65, 66, 68, 70, 72, 74, 76, 78, 80, 81, 82, 85, 86, 88, 90, 92, 93, 94, 96, 97

Offset

1,2

Links

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

Mathematica

a = {1, 2}; used = Flatten@Outer[Times, a, a] - 1; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a - 1], {n, 3, 60}]; a (* Ivan Neretin, Feb 15 2018 *)

Crossrefs

Similar sequences with different starting conditions: A026438 (1,3), A026439 (2,3), A026440 (1,4), A026441 (2,4), A026442 (3,4).

Related sequences with definition using distinct i,j: A026431 and references therein.

Sequence in context: A171946 A285385 A026435 * A026441 A047434 A062414

Adjacent sequences: A026434 A026435 A026436 * A026438 A026439 A026440

Keyword

nonn

Author

Clark Kimberling

Extensions

Terms corrected by Ivan Neretin, Feb 15 2018

Status

approved