A322456 - OEIS

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A322456

Triangle of Touchard's chord enumerating polynomial coefficients [x^k] P_n(x).

1, 1, 1, 3, 1, 4, 10, 12, 1, 5, 15, 35, 60, 77, 55, 1, 6, 21, 56, 126, 240, 391, 546, 624, 546, 273, 1, 7, 28, 84, 210, 462, 910, 1619, 2618, 3857, 5138, 6125, 6405, 5600, 3740, 1428, 1, 8, 36, 120, 330, 792, 1716, 3416, 6308, 10872, 17564, 26664, 38030, 50864, 63580, 73848, 78880, 76296, 65076, 46512, 25194, 7752

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OFFSET

1,4

LINKS

Table of n, a(n) for n=1..64.

J. Touchard, Sur un problème de configurations et sur les fractions continues, Canad. J. Math., 4 (1952), 2-25, P_n(x).

FORMULA

T(n,k) = [x^k] P_n(x), k=n*(n-1)/2 down to k=n-1.

EXAMPLE

The triangle starts

1, 3;

1, 4, 10, 12;