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A061161
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Numerators in expansion of Euler transform of b(n) = 1/4.
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3
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1, 1, 13, 55, 1235, 4615, 55801, 200343, 8977475, 36804235, 367235363, 1444888289, 32062742231, 120729974115, 1205864254225, 5201022002071, 395884671433315, 1603069490974835, 15989295873680415, 64312573140322525, 1250332447587844829, 5262481040435242585
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OFFSET
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0,3
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COMMENTS
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Denominators of c(n) are 2^A004134(n).
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LINKS
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FORMULA
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Numerators of c(n), where c(n) = (1/(4*n))*Sum_{k=1..n} c(n-k)*sigma(k), n>0, c(0)=1.
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MAPLE
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b:= proc(n) option remember; `if`(n=0, 1, add(add(
d/4, d=numtheory[divisors](j))*b(n-j), j=1..n)/n)
end:
a:= n-> numer(b(n)):
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MATHEMATICA
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c[n_] := c[n] = If[n == 0, 1,
(1/(4n)) Sum[c[n-k] DivisorSigma[1, k], {k, 1, n}]];
a[n_] := Numerator[c[n]];
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CROSSREFS
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KEYWORD
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easy,nonn,frac
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AUTHOR
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STATUS
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approved
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