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A151641 Number of permutations of 4 indistinguishable copies of 1..n with exactly 3 adjacent element pairs in decreasing order. 2
0, 16, 8464, 724320, 37229920, 1558185200, 59416090096, 2167506244544, 77394535148480, 2734912695301840, 96159966699204560, 3372863224609356576, 118169571125488257824, 4137881135327148408240, 144857367811462402307760, 5070515828676757812456320 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..200

FORMULA

a(n) = 35^n - (4*n + 1)*15^n + binomial(4*n+1, 2)*5^n - binomial(4*n+1, 3). - Andrew Howroyd, May 07 2020

PROG

(PARI) a(n) = {35^n - (4*n + 1)*15^n + binomial(4*n+1, 2)*5^n - binomial(4*n+1, 3)} \\ Andrew Howroyd, May 07 2020

CROSSREFS

Column k=3 of A236463.

Sequence in context: A280845 A069986 A265177 * A265240 A221137 A006448

Adjacent sequences:  A151638 A151639 A151640 * A151642 A151643 A151644

KEYWORD

nonn

AUTHOR

R. H. Hardin, May 29 2009

EXTENSIONS

Terms a(8) and beyond from Andrew Howroyd, May 07 2020

STATUS

approved

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Last modified July 6 11:37 EDT 2022. Contains 355110 sequences. (Running on oeis4.)