A026426 a(n) = least positive integer > a(n-1) and not a(i)*a(j) for 1<=i<=j<=n, n >= 2.

2, 4, 5, 6, 7, 9, 11, 13, 15, 17, 19, 21, 23, 27, 29, 31, 32, 33, 37, 39, 40, 41, 43, 47, 48, 50, 51, 53, 56, 57, 59, 61, 67, 69, 70, 71, 72, 73, 79, 83, 87, 88, 89, 93, 97, 98, 101, 103, 104, 107, 109, 110, 111, 113, 120, 123, 125, 127

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Links

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

Crossrefs

Cf. A026416 and references therein.

Programs

Mathematica

a = {2, 4}; used = {a[[1]]^2, a[[1]]*a[[2]], a[[2]]^2}; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a], {n, 3, 66}]; a (* Ivan Neretin, Mar 07 2016 *)