The On-Line Encyclopedia of Integer Sequences (OEIS)

Revision History for A230033 (Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
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A230033

Number of perfect matchings in the graph C_7 X C_{2n}.
(history; published version)

#23 by Alois P. Heinz at Sun Feb 28 08:22:02 EST 2021

STATUS

proposed

approved

#22 by Seiichi Manyama at Sun Feb 28 08:08:58 EST 2021

STATUS

editing

proposed

#21 by Seiichi Manyama at Sun Feb 28 07:19:19 EST 2021

LINKS

Seiichi Manyama, <a href="/A230033/b230033.txt">Table of n, a(n) for n = 2..500</a>

#20 by Seiichi Manyama at Sun Feb 28 06:36:58 EST 2021

CROSSREFS

Cf. A231087, A220864, A231485, A232804, A281583, A308761.

#19 by Seiichi Manyama at Sun Feb 28 06:25:48 EST 2021

CROSSREFS

Column k=7 of A341533.

STATUS

approved

editing

#18 by N. J. A. Sloane at Sun Feb 14 04:43:15 EST 2021

STATUS

proposed

approved

#17 by Seiichi Manyama at Sun Feb 14 04:24:06 EST 2021

STATUS

editing

proposed

#16 by Seiichi Manyama at Sun Feb 14 01:29:21 EST 2021

FORMULA

a(n) = sqrt( Product_{j=1..n} Product_{k=1..7} (4*sin((2*j-1)*Pi/(2*n))^2 + 4*sin((2*k-1)*Pi/7)^2) ). - _Seiichi Manyama_, Feb 14 2021

#15 by Seiichi Manyama at Sun Feb 14 01:23:48 EST 2021

FORMULA

a(n) = sqrt( Product_{j=1..n} Product_{k=1..7} (4*sin((2*j-1)*Pi/(2*n))^2 + 4*sin((2*k-1)*Pi/7)^2) ).

#14 by Seiichi Manyama at Sun Feb 14 00:54:00 EST 2021

PROG

(PARI) default(realprecision, 120);

a(n) = round(sqrt(prod(j=1, n, prod(k=1, 7, 4*sin((2*j-1)*Pi/(2*n))^2+4*sin((2*k-1)*Pi/7)^2)))); \\ Seiichi Manyama, Feb 14 2021

STATUS

approved

editing