A026439 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2.

2, 3, 4, 6, 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, 81, 82, 84, 85, 86, 88, 90, 92, 93, 94, 96, 100, 102

Offset

1,1

Links

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

Mathematica

a = {2, 3}; 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.

Sequence in context: A356896 A111251 A047300 * A285082 A249602 A119761

Adjacent sequences: A026436 A026437 A026438 * A026440 A026441 A026442

Keyword

nonn

Author

Clark Kimberling

Status

approved