A026431 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1<=i<j<=n.

1, 2, 3, 4, 6, 8, 9, 10, 12, 13, 14, 16, 18, 20, 21, 22, 24, 28, 30, 32, 33, 34, 36, 37, 40, 42, 44, 45, 46, 48, 49, 50, 52, 54, 56, 57, 58, 60, 61, 64, 66, 68, 69, 70, 72, 74, 75, 76, 78, 80, 81, 82, 84, 85, 86, 88, 90, 92, 93, 94

Offset

1,2

Links

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

Mathematica

a = {1, 2}; 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 06 2016 *)

Crossrefs

Similar sequences with different starting conditions: A026432 (1,3), A026433 (2,3), A026434 (1,4), A026435 (2,4), A026436 (3,4).

Sequence in context: A377078 A352968 A156657 * A026433 A354148 A015858

Adjacent sequences: A026428 A026429 A026430 * A026432 A026433 A026434

Keyword

nonn

Author

Clark Kimberling

Status

approved