A049646 a(n) = T(n,n+1), array T given by A049639.

0, 1, 3, 4, 5, 7, 9, 11, 13, 17, 21, 23, 25, 31, 37, 41, 45, 51, 57, 61, 65, 75, 85, 89, 93, 105, 117, 123, 129, 137, 145, 153, 161, 177, 193, 199, 205, 223, 241, 249, 257, 269, 281, 291, 301, 323, 345, 353, 361, 381, 401, 413, 425, 443, 461, 473, 485, 513, 541, 549, 557

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 0..75

Crossrefs

Cf. A049639.

Programs

Mathematica

a[0 | 1, 0 | 1] = 0; a[0 | 1, ] = a[, 0 | 1] = 1; a[i_, j_] := Module[{slopes, cnt}, slopes = Union@Flatten@Table[(k - j)/(h - i), {h, 0, i - 1}, {k, 0, j - 1}]; cnt[slope_] := Count[Flatten[Table[{h, k}, {h, 0, i - 1}, {k, 0, j - 1}], 1], {h_, k_} /; (k - j)/(h - i) == slope]; Count[cnt /@ slopes, c_ /; c >= 2] + 2]; Table[a[n, n + 1], {n, 0, 25}] (* G. C. Greubel, Dec 07 2017 *)

Extensions

Terms a(39)-a(60) added by G. C. Greubel, Dec 07 2017