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A170920
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Write cot(x) = Prod_{n>=1} (1 + g_n x^2n); a(n) = numerator(g_n).
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1
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-1, -2, -211, -2743, -1418638, -2268068, -550669394, -23861846102, -48726978122069, -461240499534601, -336080282371649483, -2842820955735934463, -1628158082048867402632, -331277549738199913530049, -14001180998026101838535141, -1500970948062470951644822898, -889277588648296174667504384505014
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..17.
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EXAMPLE
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-1/3, -2/27, -211/3645, -2743/98415, -1418638/93002175, ...
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MAPLE
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t1:=cot(x);
L:=100;
t0:=series(t1, x, L):
g:=[];
M:=20; # number of terms to get
t2:=t0:
for n from 1 to M do
t3:=coeff(t2, x, n); t2:=series(t2/(1+t3*x^n), x, L); g:=[op(g), t3];
od:
g;
g1:=map(numer, g);
g2:=map(denom, g);
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CROSSREFS
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Cf. A170921, A170908-A170919.
Sequence in context: A167839 A107612 A068814 * A215641 A195335 A090560
Adjacent sequences: A170917 A170918 A170919 * A170921 A170922 A170923
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KEYWORD
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sign,frac
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AUTHOR
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N. J. A. Sloane, Jan 31 2010
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STATUS
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approved
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