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A173850 Number of permutations of 1..n with no adjacent pair summing to n+10. 0
1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880, 3628800, 32659200, 399168000, 4470681600, 64186214400, 855496857600, 14073067008000, 216999220838400, 4018570511155200, 70276861528473600, 1445722935681024000, 28251875803447296000, 638889942904012800000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

If a(n,k) is the number of permutations of 1..n with no adjacent pair summing to n+k, then a(n,k) = a(n,k+1) for n+k even.

LINKS

Table of n, a(n) for n=0..22.

FORMULA

k = 10; m = max(0, floor((n-k+1)/2)); a(n,k) = Sum_{j=0..m} (-2)^j * binomial(m,j)*(n-j)!.

CROSSREFS

Sequence in context: A276844 A273697 A177281 * A154658 A179369 A267390

Adjacent sequences:  A173847 A173848 A173849 * A173851 A173852 A173853

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 26 2010

EXTENSIONS

Comment proved by William Keith, formula from Max Alekseyev, on the Sequence Fans Mailing List

More terms from Alois P. Heinz, Jan 09 2017

STATUS

approved

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Last modified December 8 04:31 EST 2019. Contains 329850 sequences. (Running on oeis4.)