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 A029697 Number of words of length 2n in the 6 transpositions of S[ 4 ] equivalent to the identity. 1
 6, 120, 3936, 140160, 5039616, 181401600, 6530359296, 235092541440, 8463329918976, 304679870791680, 10968475323334656, 394865111539384320, 14215144015015182336, 511745184538935951360, 18422826643395251798016, 663221759162203294924800 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..300 Index entries for linear recurrences with constant coefficients, signature (40,-144). FORMULA a(n) = (9*4^n+36^n)/12. a(n) = 40*a(n-1)-144*a(n-2). - Colin Barker, May 28 2015 G.f.: -6*x*(20*x-1) / ((4*x-1)*(36*x-1)). - Colin Barker, May 28 2015 PROG (MAGMA) [(9*4^n+36^n)/12: n in [1..15]]; // Vincenzo Librandi, Jun 30 2011 (PARI) Vec(-6*x*(20*x-1) / ((4*x-1)*(36*x-1)) + O(x^100)) \\ Colin Barker, May 28 2015 CROSSREFS Sequence in context: A246611 A185757 A075844 * A248045 A280627 A196688 Adjacent sequences:  A029694 A029695 A029696 * A029698 A029699 A029700 KEYWORD nonn,easy AUTHOR Paolo Dominici (pl.dm(AT)libero.it) STATUS approved

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Last modified May 21 00:36 EDT 2022. Contains 353886 sequences. (Running on oeis4.)