A026442 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2.

3, 4, 5, 6, 7, 9, 10, 12, 13, 16, 18, 21, 22, 25, 28, 30, 31, 32, 33, 36, 37, 40, 42, 43, 45, 46, 50, 52, 54, 55, 56, 57, 58, 60, 61, 66, 67, 68, 70, 72, 73, 75, 76, 78, 81, 82, 84, 85, 86, 88, 91, 93, 94, 96, 97, 100, 101, 102, 103, 105

Offset

1,1

Comments

a(n) = A026438(n+1) for n > 1. - Georg Fischer, Oct 22 2018

Links

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

Mathematica

a = {3, 4}; 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

Cf. A026437 and references therein.

Cf. A026438.

Sequence in context: A083121 A298006 A026438 * A334763 A307712 A048869

Adjacent sequences: A026439 A026440 A026441 * A026443 A026444 A026445

Keyword

nonn

Author

Clark Kimberling

Status

approved