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A170920 Write x*cot(x) = Product_{n>=1} (1 + g_n*x^(2*n)); a(n) = numerator(g_n). 1
-1, -1, -1, -16, -91, -58844, -73267, -1196588, -49830764, -1715330699, -35249288479, -374085503198546, -732125336837021, -779432268293710651, -30015706187367326893, -183998031852529374082, -46789354983174555461, -115977125342651266593554, -248130101882943187003954597, -13171311382437535379302071714878 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

-1/3, -1/45, -1/105, -16/4725, -91/66825, -58844/127702575, -73267/383107725, ...

MAPLE

t1:=x*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, 2*n); t2:=series(t2/(1+t3*x^(2*n)), x, L); g:=[op(g), t3];

od:

g;

g1:=map(numer, g);

g2:=map(denom, g);

CROSSREFS

Cf. A170921, A170908-A170919.

Sequence in context: A050406 A047674 A153029 * A027938 A301527 A185458

Adjacent sequences:  A170917 A170918 A170919 * A170921 A170922 A170923

KEYWORD

sign,frac

AUTHOR

N. J. A. Sloane, Jan 31 2010

EXTENSIONS

Corrected definition and terms - N. J. A. Sloane, Oct 04 2019 (thanks to Petros Hadjicostas for pointing out that something was wrong).

STATUS

approved

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Last modified January 18 15:25 EST 2021. Contains 340254 sequences. (Running on oeis4.)