A026479 a(n) = least positive integer > a(n-1) and not a(i)*a(j)*a(k) for 1<=i

1, 2, 4, 5, 6, 7, 9, 11, 13, 15, 16, 17, 19, 21, 23, 25, 27, 29, 31, 33, 37, 39, 41, 43, 47, 49, 51, 53, 57, 59, 61, 67, 69, 71, 73, 79, 81, 83, 87, 89, 93, 97, 101, 103, 107, 109, 111, 113, 121, 123, 127, 129, 131, 137, 139, 141, 149, 151, 157, 159, 163

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

• Robert Price, Table of n, a(n) for n = 1..203

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, 2, 4}; no = {1 2 4};
Do[x = SelectFirst[Range[Last[a] + 1, 1000], ! MemberQ[no, #] &]; AppendTo[a, x]; no = Union[Times @@@ Subsets[a, {3}]], 200]; a (* Robert Price, May 26 2019 *)

Extensions

a(31)-a(61) from Robert Price, May 26 2019