A026436 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1<=i<j<=n, with initial terms 3,4.

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

1,1

Links

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

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 *)

Crossrefs

Cf. A026431 and references therein.

Sequence in context: A039238 A299532 A026432 * A026452 A271928 A039157

Adjacent sequences: A026433 A026434 A026435 * A026437 A026438 A026439

Keyword

nonn

Author

Clark Kimberling

Extensions

Name clarified by Robert C. Lyons, Feb 06 2025

Status

approved