A026481 a(n) = least positive integer > a(n-1) and not a(i)*a(j)*a(k) for 1<=i

1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 13, 14, 16, 17, 19, 22, 23, 25, 26, 29, 31, 34, 37, 38, 41, 43, 46, 47, 49, 53, 58, 59, 61, 62, 67, 71, 73, 74, 79, 81, 82, 83, 86, 89, 94, 97, 101, 103, 106, 107, 109, 113, 118, 121, 122, 127, 131, 134, 137, 139, 142, 146, 149, 151, 157

Offset: 1

Author

Clark Kimberling

Keywords

• nonn
• easy

Crossrefs

There are six related sequences: A026477: 1 <= i < j < k < n starting 1,2,3; A026478: 1 <= i <= j <= k < n starting 1,2,3; A026479: 1 <= i < j < k < n starting 1,2,4; A026480: 1 <= i <= j <= k < n starting 1,2,4; A026481: 1 <= i < j < k < n starting 1,3,4; A026482: 1 <= i <= j <= k < n starting 1,3,4.

Programs

Mathematica

a = {1, 3, 4}; no = {1 3 4};
Do[x = SelectFirst[Range[Last[a] + 1, 1000], ! MemberQ[no, #] &]; AppendTo[a, x]; no = Union[Times @@@ Subsets[a, {3}]], 62]; a (* Robert Price, May 26 2019 *)

Extensions

More terms from Todd Will (towill(AT)davidson.edu).