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 A231621 a(n) = A000930(n*(n+1)/2), where A000930 is Narayana's cows sequence. 2
 1, 1, 2, 6, 28, 189, 1873, 27201, 578949, 18059374, 825604416, 55315679788, 5431645680297, 781666575692345, 164861247948842305, 50959194632488457965, 23085190353310504913320, 15326793132326730009566200, 14913379277290330452859885202, 21267074956884103635776195255433, 44447403127130268192387935737712641 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS G. C. Greubel, Table of n, a(n) for n = 0..100 FORMULA a(n) = [x^(n*(n+1)/2)] 1 / (1 - x - x^3) for n>=0. MATHEMATICA Table[SeriesCoefficient[1/(1 - x - x^3), {x, 0, n*(n + 1)/2}], {n, 0, 50}] (* G. C. Greubel, Apr 26 2017 *) PROG (PARI) {a(n) = polcoeff(1/(1-x-x^3 + x*O(x^(n*(n+1)/2))), n*(n+1)/2)} for(n=0, 20, print1(a(n), ", ")) CROSSREFS Cf. A000930, A231620. Sequence in context: A355205 A196555 A084262 * A084870 A111342 A008964 Adjacent sequences:  A231618 A231619 A231620 * A231622 A231623 A231624 KEYWORD nonn AUTHOR Paul D. Hanna, Nov 13 2013 STATUS approved

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Last modified August 7 23:50 EDT 2022. Contains 355995 sequences. (Running on oeis4.)