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A349021
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G.f. satisfies A(x) = 1/(1 - x/(1 - x*A(x))^2)^4.
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1
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1, 4, 18, 104, 671, 4624, 33342, 248412, 1897219, 14774152, 116864936, 936390692, 7584216152, 61992689940, 510728310716, 4236545121924, 35354229533389, 296604036437692, 2500154435955614, 21164005790766980, 179841032283906149, 1533499916749203208
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OFFSET
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0,2
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LINKS
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FORMULA
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If g.f. satisfies: A(x) = 1/(1 - x/(1 - x*A(x))^s)^t, then a(n) = Sum_{k=0..n} binomial(t*n-(t-1)*(k-1),k) * binomial(n+(s-1)*k-1,n-k)/(n-k+1).
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MAPLE
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local s, t ;
s := 2 ;
t := 4;
add( binomial(t*n-(t-1)*(k-1), k) * binomial(n+(s-1)*k-1, n-k) /(n-k+1) , k=0..n) ;
end proc:
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PROG
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(PARI) a(n, s=2, t=4) = sum(k=0, n, binomial(t*n-(t-1)*(k-1), k)*binomial(n+(s-1)*k-1, n-k)/(n-k+1));
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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