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 A011779 Expansion of 1/((1-x)^3*(1-x^3)^2). 4
 1, 3, 6, 12, 21, 33, 51, 75, 105, 145, 195, 255, 330, 420, 525, 651, 798, 966, 1162, 1386, 1638, 1926, 2250, 2610, 3015, 3465, 3960, 4510, 5115, 5775, 6501, 7293, 8151, 9087, 10101, 11193, 12376, 13650 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The Ca2 and Ze4 triangle sums of A139600 are related to the sequence given above, e.g., Ze4(n) = A011779(n-1) - A011779(n-2) - A011779(n-4) + 3*A011779(n-5), with A011779(n) = 0 for n <= -1. For the definitions of these triangle sums see A180662. [Johannes W. Meijer, Apr 29 2011] LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Project Euler, Problem 577. Counting hexagons. Index entries for linear recurrences with constant coefficients, signature (3,-3,3,-6,6,-3,3,-3,1). MATHEMATICA CoefficientList[Series[1 / ((1 - x)^3 (1 - x^3)^2), {x, 0, 100}], x] (* Vincenzo Librandi, Jun 23 2013 *) PROG (PARI) Vec(1/((1-x)^3*(1-x^3)^2)+O(x^99)) \\ Charles R Greathouse IV, Sep 25 2012 (PARI) a(n)=1/216 * n^4 + 1/12 * n^3 + 37/72 * n^2 + [5/4, 139/108, 131/108][1+n%3] * n + [1, 10/9, 7/9][1+n%3] \\ Yurii Ivanov, Jul 06 2021 CROSSREFS Cf. A236770 (first trisection, except 0). Sequence in context: A053479 A290768 A070333 * A161809 A084439 A034344 Adjacent sequences:  A011776 A011777 A011778 * A011780 A011781 A011782 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified June 26 18:18 EDT 2022. Contains 354885 sequences. (Running on oeis4.)