A228647
a(n) = A001609(n^2) for n>=1, where g.f. of A001609 is x*(1+3*x^2)/(1-x-x^3).
Original entry on oeis.org
1, 5, 31, 453, 14131, 946781, 136250983, 42115660581, 27961563559891, 39874307297033165, 122134599693975367423, 803522677430288749340325, 11354589189995520431547851761, 344634362031276605039944979868611, 22467750416780812361715214948922598721, 3146114090698891414621617889648190060326821
Offset: 1
L.g.f.: L(x) = x + 5*x^2/2 + 31*x^3/3 + 453*x^4/4 + 14131*x^5/5 +...
where
exp(L(x)) = 1 + x + 3*x^2 + 13*x^3 + 128*x^4 + 2974*x^5 + 161048*x^6 + 19632276*x^7 +...+ A228648(n)*x^n +...
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{A001609(n)=n*polcoeff(-log(1-x-x^3 +x*O(x^n)), n)}
{a(n)=A001609(n^2)}
for(n=1,20,print1(a(n),", "))
A231621
a(n) = A000930(n*(n+1)/2), where A000930 is Narayana's cows sequence.
Original entry on oeis.org
1, 1, 2, 6, 28, 189, 1873, 27201, 578949, 18059374, 825604416, 55315679788, 5431645680297, 781666575692345, 164861247948842305, 50959194632488457965, 23085190353310504913320, 15326793132326730009566200, 14913379277290330452859885202, 21267074956884103635776195255433, 44447403127130268192387935737712641
Offset: 0
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Table[SeriesCoefficient[1/(1 - x - x^3), {x, 0, n*(n + 1)/2}], {n,0,50}] (* G. C. Greubel, Apr 26 2017 *)
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{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), ", "))
Showing 1-2 of 2 results.
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