A231621 a(n) = A000930(n*(n+1)/2), where A000930 is Narayana's cows sequence.

1, 1, 2, 6, 28, 189, 1873, 27201, 578949, 18059374, 825604416, 55315679788, 5431645680297, 781666575692345, 164861247948842305, 50959194632488457965, 23085190353310504913320, 15326793132326730009566200, 14913379277290330452859885202, 21267074956884103635776195255433, 44447403127130268192387935737712641

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