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 A317527 Number of edges in the n-alternating group graph. 2
 0, 0, 3, 24, 180, 1440, 12600, 120960, 1270080, 14515200, 179625600, 2395008000, 34248614400, 523069747200, 8499883392000, 146459529216000, 2667655710720000, 51218989645824000, 1033983353475072000, 21896118073589760000, 485363950631239680000, 11240007277776076800000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Looks like the denominators of g.f.: (1-x)*exp(-x) + x^2*(Chi(x) - Shi(x)), for cosh and sinh integral functions. - Benedict W. J. Irwin, Jun 04 2018 LINKS Table of n, a(n) for n=1..22. Eric Weisstein's World of Mathematics, Alternating Group Graph Eric Weisstein's World of Mathematics, Edge Count FORMULA a(n) = n!*(n - 2)/2 for n > 1. a(n) = 3 * A005990(n-1) for n>1. - Alois P. Heinz, Jul 30 2018 E.g.f.: x^3/(2*(x - 1)^2). MATHEMATICA Join[{0}, Table[n! (n - 2)/2, {n, 2, 20}]] CoefficientList[Series[x^2/(2 (-1 + x)^2), {x, 0, 19}], x] Range[20]! PROG (Magma) [0] cat [Factorial(n)*(n-2)/2: n in [2..25]]; // Vincenzo Librandi, Jul 31 2018 CROSSREFS Cf. A005990, A181967. Sequence in context: A292293 A073985 A197209 * A181967 A144087 A110347 Adjacent sequences: A317524 A317525 A317526 * A317528 A317529 A317530 KEYWORD nonn AUTHOR Eric W. Weisstein, Jul 30 2018 STATUS approved

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Last modified December 3 02:05 EST 2023. Contains 367530 sequences. (Running on oeis4.)