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 A152257 a(n) = (3^n - 1)^2*(3^n + 1)/16. 1
 0, 1, 40, 1183, 32800, 893101, 24180520, 653473003, 17649155200, 476575627801, 12867977828200, 347439324082423, 9380897054183200, 253284538196972101, 6838685390919695080, 184644531291230453443, 4985402576490767372800, 134605871649898496094001 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Robert Israel, Table of n, a(n) for n = 0..698 Index entries for linear recurrences with constant coefficients, signature (40,-390,1080,-729). FORMULA a(n)=(3^n - 1)*(3^n + 1)*(3^n - 1)/16. G.f.: x*(1-27*x^2)/((1-x)*(1-3*x)*(1-9*x)*(1-27*x)). - Robert Israel, Mar 18 2019 a(n) = 40*a(n-1) - 390*a(n-2) + 1080*a(n-3) - 729*a(n-4) for n>3. - Colin Barker, Mar 18 2019 MAPLE seq((3^n-1)^2*(3^n+1)/16, n=0..30); # Robert Israel, Mar 18 2019 MATHEMATICA Clear[a, n]; a[n_] := (3^n - 1)*(3^n + 1)*(3^n - 1)/16 Table[a[n], {n, 0, 30}] PROG (PARI) concat(0, Vec(x*(1 - 27*x^2) / ((1 - x)*(1 - 3*x)*(1 - 9*x)*(1 - 27*x)) + O(x^20))) \\ Colin Barker, Mar 18 2019 CROSSREFS Cf. A003462, A002452. Sequence in context: A331906 A144914 A004385 * A229457 A331350 A061650 Adjacent sequences:  A152254 A152255 A152256 * A152258 A152259 A152260 KEYWORD nonn,easy AUTHOR Roger L. Bagula, Dec 01 2008 EXTENSIONS 0 inserted by Robert Israel, Mar 18 2019 STATUS approved

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Last modified February 27 22:38 EST 2020. Contains 332312 sequences. (Running on oeis4.)