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A341851 Number of maximum matchings in the 3 X n rook graph. 4
1, 3, 4, 72, 132, 7020, 17280, 1920240, 6022800, 1154366640, 4421511360, 1303028052480, 5906331224640, 2481613890275520, 13003380449579520, 7385997122881977600, 43944212734316294400, 32440254625217626387200, 216088204725662645376000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..100

PROG

(PARI) a(n)={my(v=vector((n+1)\2+1, i, i--; (2*i)!/(2^i*i!))); if(n%2, 3, 1)*sum(i=0, n\2, sum(j=0, n\2, sum(k=abs(i-j), min(i+j, n-i-j), n!/((i+k-j)!*(i+j-k)!*(n-i-j-k)!*(j+k-i)!)*v[1+(n+1)\2-i]*v[1+j]*v[1+k] )))} \\ Andrew Howroyd, Mar 14 2021

CROSSREFS

Row n=3 of A341850.

Cf. A341502, A341848.

Sequence in context: A012087 A012194 A318208 * A132414 A041171 A279935

Adjacent sequences: A341848 A341849 A341850 * A341852 A341853 A341854

KEYWORD

nonn

AUTHOR

Andrew Howroyd, Feb 21 2021

STATUS

approved

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Last modified January 29 02:42 EST 2023. Contains 359915 sequences. (Running on oeis4.)