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A366118
Expansion of (1/x) * Series_Reversion( x*(1+x+x^3)/(1+x)^4 ).
4
1, 3, 12, 54, 259, 1292, 6616, 34507, 182395, 973691, 5236794, 28323936, 153842660, 838210232, 4577088300, 25029752243, 136984351418, 749861003157, 4103514165744, 22437771907824, 122529735856669, 667928556599614, 3632677249330084, 19701490439727844
OFFSET
0,2
COMMENTS
a(40) is negative.
LINKS
FORMULA
a(n) = (1/(n+1)) * Sum_{k=0..floor(n/3)} (-1)^k * binomial(n+k,k) * binomial(3*n-k+3,n-3*k).
PROG
(PARI) a(n) = sum(k=0, n\3, (-1)^k*binomial(n+k, k)*binomial(3*n-k+3, n-3*k))/(n+1);
CROSSREFS
KEYWORD
sign
AUTHOR
Seiichi Manyama, Sep 29 2023
STATUS
approved