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A151610 Number of permutations of 7 indistinguishable copies of 1..n arranged in a circle with exactly 2 adjacent element pairs in decreasing order. 3
0, 252, 4935, 56560, 572215, 5503260, 51377823, 469758912, 4227854463, 37580958940, 330712475863, 2886218015856, 25013889523623, 215504279034492, 1847179534652655, 15762598695784192, 133982088914258095, 1134907106097349116, 9583660007044397799, 80704505322479268720 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
FORMULA
a(n) = n*((7/2)*8^n - 49*n) for n > 1. - Andrew Howroyd, May 04 2020
From Colin Barker, Jul 16 2020: (Start)
G.f.: 7*x^2*(36 + 21*x - 1175*x^2 + 624*x^3 - 192*x^4) / ((1 - x)^3*(1 - 8*x)^2).
a(n) = 19*a(n-1) - 115*a(n-2) + 241*a(n-3) - 208*a(n-4) + 64*a(n-5) for n>6.
(End)
PROG
(PARI) a(n) = if(n <= 1, 0, n*(7*8^n/2 - 49*n)) \\ Andrew Howroyd, May 04 2020
(PARI) concat(0, Vec(7*x^2*(36 + 21*x - 1175*x^2 + 624*x^3 - 192*x^4) / ((1 - x)^3*(1 - 8*x)^2) + O(x^20))) \\ Colin Barker, Jul 16 2020
CROSSREFS
Cf. A151583.
Sequence in context: A184498 A169713 A099059 * A250085 A024018 A270853
KEYWORD
nonn,easy
AUTHOR
R. H. Hardin, May 21 2009
EXTENSIONS
Terms a(7) and beyond from Andrew Howroyd, May 04 2020
STATUS
approved

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Last modified April 24 20:08 EDT 2024. Contains 371963 sequences. (Running on oeis4.)