A026464 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-2 for 1<=i<=j<=n.

3, 4, 5, 6, 8, 9, 11, 12, 15, 17, 19, 20, 21, 24, 26, 27, 29, 32, 33, 35, 36, 37, 39, 40, 41, 44, 45, 47, 48, 50, 51, 54, 56, 57, 59, 60, 63, 65, 67, 68, 69, 71, 72, 75, 77, 80, 81, 84, 87, 89, 90, 91, 92, 95, 96, 99, 101, 104, 105, 107

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Comments

Essentially the same as A026460. [From R. J. Mathar, Oct 23 2008]

Links

• Christopher R. H. Hanusa, T Zaslavsky, S Chaiken, A q-Queens Problem. IV. Queens, Bishops, Nightriders (and Rooks), arXiv preprint arXiv:1609.00853, a12016

Programs

Mathematica

a[1] = 3; a[2] = 4; a[n_] := a[n] =
For[k = a[n-1]+1, True, k++, a[n] = k; If[AllTrue[Tuples[Range[n], {2}], k != a[#[[1]]] a[#[[2]]] - 2&], Return[k]]
];
Array[a, 60] (* Jean-François Alcover, Oct 30 2018 *)