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 A173848 Number of permutations of 1..n with no adjacent pair summing to n + 8. 0
 1, 1, 2, 6, 24, 120, 720, 5040, 40320, 282240, 2903040, 26853120, 333849600, 3802982400, 55244851200, 745007155200, 12362073292800, 192275074252800, 3584572069478400, 63107717389516800, 1305169212624076800, 25641537378199142400, 582386191297118208000 (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 FORMULA k = 8; 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: A276842 A273695 A177279 * A154656 A179354 A179360 Adjacent sequences:  A173845 A173846 A173847 * A173849 A173850 A173851 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 January 21 13:55 EST 2020. Contains 331113 sequences. (Running on oeis4.)