A026436 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1<=i

3, 4, 5, 6, 7, 8, 9, 10, 12, 13, 15, 16, 18, 21, 22, 24, 25, 28, 30, 32, 33, 36, 37, 40, 42, 43, 45, 46, 48, 50, 52, 54, 56, 57, 58, 60, 61, 66, 67, 68, 70, 72, 73, 75, 76, 78, 80, 81, 82, 84, 85, 86, 88, 91, 92, 93, 94, 96, 97, 100

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

Appears to be A026432 shifted left. - R. J. Mathar, Jun 24 2025

Links

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

Crossrefs

Cf. A026431 and references therein.

Programs

Mathematica

a = {3, 4}; used = {a[[1]]*a[[2]] - 1}; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; used = Union[used, k*a - 1]; AppendTo[a, k], {n, 3, 60}]; a (* Ivan Neretin, Mar 07 2016 *)

Extensions

Name clarified by Robert C. Lyons, Feb 06 2025