A026447 a(n) = least positive integer > a(n-1) and not a(i)*a(j)+2 for 1<=i

3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 18, 19, 21, 24, 25, 27, 28, 31, 33, 36, 39, 40, 43, 45, 48, 49, 51, 53, 55, 60, 61, 63, 64, 69, 70, 71, 73, 75, 76, 81, 84, 85, 87, 88, 89, 91, 94, 96, 99, 100, 103, 104, 105, 108, 109, 111, 113

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

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

Crossrefs

Cf. A026443 and references therein.

Programs

Mathematica

a = {3, 4}; 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 *)

Extensions

Name clarified by Robert C. Lyons, Feb 07 2025