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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

%I

%S 0,16,8464,724320,37229920,1558185200,59416090096,2167506244544,

%T 77394535148480,2734912695301840,96159966699204560,

%U 3372863224609356576,118169571125488257824,4137881135327148408240,144857367811462402307760,5070515828676757812456320

%N Number of permutations of 4 indistinguishable copies of 1..n with exactly 3 adjacent element pairs in decreasing order.

%H Andrew Howroyd, <a href="/A151641/b151641.txt">Table of n, a(n) for n = 1..200</a>

%F 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

%o (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

%Y Column k=3 of A236463.

%K nonn

%O 1,2

%A _R. H. Hardin_, May 29 2009

%E Terms a(8) and beyond from _Andrew Howroyd_, May 07 2020

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Last modified August 15 09:19 EDT 2022. Contains 356135 sequences. (Running on oeis4.)