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 A256960 a(0)=1, a(1)=4; thereafter a(n) = a(n-2)+2*A055099(n-1)+2^(n-1). 1
 1, 4, 11, 36, 119, 408, 1419, 4988, 17631, 62528, 222163, 790180, 2812135, 10011304, 35647259, 126942540, 452078447, 1610033040, 5734081251, 20421960308, 72733344375, 259042555640, 922591559467, 3285854197276, 11702734525951, 41679889602784, 148445093121011, 528694969090116 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Colin Barker, Table of n, a(n) for n = 0..1000 J. Goldwasser et al., The density of ones in Pascal's rhombus, Discrete Math., 204 (1999), 231-236. Paul K. Stockmeyer, The Pascal Rhombus and the Stealth Configuration, arXiv:1504.04404 [math.CO], 2015. Index entries for linear recurrences with constant coefficients, signature (4,1,-8,-4). FORMULA G.f.: -(2*x+1)*(2*x^2+2*x-1) / ((x+1)*(2*x-1)*(2*x^2+3*x-1)). - Colin Barker, Jun 05 2015 PROG (PARI) Vec(-(2*x+1)*(2*x^2+2*x-1)/((x+1)*(2*x-1)*(2*x^2+3*x-1)) + O(x^100)) \\ Colin Barker, Jun 06 2015 CROSSREFS Cf. A055099. Sequence in context: A206687 A106640 A109268 * A174993 A149238 A149239 Adjacent sequences:  A256957 A256958 A256959 * A256961 A256962 A256963 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Apr 14 2015 STATUS approved

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Last modified October 16 15:51 EDT 2019. Contains 328101 sequences. (Running on oeis4.)