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A049640 a(n) = Sum_{i=0..n} T(i,n-i), array T as in A049639. 1
0, 0, 2, 4, 7, 10, 15, 20, 27, 34, 45, 56, 69, 82, 101, 120, 143, 166, 195, 224, 257, 290, 333, 376, 423, 470, 529, 588, 653, 718, 791, 864, 945, 1026, 1123, 1220, 1323, 1426, 1547, 1668, 1797, 1926, 2067, 2208, 2359, 2510, 2683, 2856, 3037, 3218, 3419, 3620, 3833, 4046, 4277, 4508 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

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[Sum[a[k, n - k], {k, 0, n}], {n, 0, 25}] (* G. C. Greubel, Dec 15 2017 *)

CROSSREFS

Sequence in context: A022939 A036702 A007983 * A179385 A024668 A188951

Adjacent sequences:  A049637 A049638 A049639 * A049641 A049642 A049643

KEYWORD

nonn

AUTHOR

Clark Kimberling

EXTENSIONS

Terms a(41) and beyond added by G. C. Greubel, Dec 15 2017

STATUS

approved

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Last modified October 14 02:29 EDT 2019. Contains 327995 sequences. (Running on oeis4.)