A323535 a(n) = Product_{k=1..n} (binomial(k-1,7) + binomial(n-k,7)).

1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 240248274716697412239360000, 5659588189073370681080838881280000, 148305406398618918682372310424354816000000, 4049882681498254991937037064898924144230400000000, 137651993399006086593846978063252515678682995490816000000

Offset

0,15

Links

Table of n, a(n) for n=0..18.

Formula

a(n) ~ exp(-7*n + (n-7)*(1 + c*Pi)) * n^(7*n) / (7!)^n, where c = 8*cos((Pi + arctan(2769*sqrt(3)/239))/6) / sqrt(21) = 1.2446281707164555154936427017... is the root of the equation 823543*c^6 - 3764768*c^4 + 4302592*c^2 - 692224 = 0.

Mathematica

Table[Product[Binomial[k-1, 7] + Binomial[n-k, 7], {k, 1, n}], {n, 0, 20}]

Prog

(PARI) a(n) = prod(k=1, n, binomial(k-1, 7) + binomial(n-k, 7)); \\ Daniel Suteu, Jan 17 2019

Crossrefs

Cf. A000580, A323425, A323496, A323497, A323533, A323534.

Sequence in context: A217410 A338956 A338952 * A250493 A219322 A280349

Adjacent sequences: A323532 A323533 A323534 * A323536 A323537 A323538

Keyword

nonn

Author

Vaclav Kotesovec, Jan 17 2019

Status

approved