A049649 T(n,n+3), array T given by A049639.

1, 1, 4, 5, 7, 8, 11, 14, 17, 18, 23, 28, 31, 34, 41, 46, 51, 54, 61, 70, 75, 78, 89, 100, 105, 110, 123, 130, 137, 144, 153, 168, 177, 182, 199, 216, 223, 230, 249, 260, 269, 278, 291, 312, 323, 330, 353, 372, 381, 392, 413, 430, 443, 454, 473, 500, 513, 520, 549, 578, 587, 602

Offset: 0

Author

Clark Kimberling

Keywords

• nonn

Links

• Sean A. Irvine, Table of n, a(n) for n = 0..500 (terms 1..76 from G. C. Greubel)

Crossrefs

Cf. A049639.

Programs

Mathematica

T[0 | 1, 0 | 1] = 0; T[0 | 1, ] = T[, 0 | 1] = 1; T[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[T[n, n + 3], {n, 0, 50}] (* G. C. Greubel, Dec 05 2017 *)

Extensions

Terms a(37) onward added by G. C. Greubel, Dec 10 2017

Missing a(0)=1 inserted by Sean A. Irvine, Aug 06 2021