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A295758 O.g.f.: Sum_{n>=0} Product_{k=1..n} tan( (2*k-1)*arctan(x) ). 1
1, 1, 3, 15, 113, 1105, 13219, 187103, 3058113, 56675297, 1174295267, 26898243439, 674916701169, 18409502066097, 542373965958595, 17164148092886207, 580677914417571585, 20913258579319759041, 798876414332323236931, 32261582928825038942671, 1373304514339211081661169 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..20.

EXAMPLE

O.g.f: A(x) = 1 + x + 3*x^2 + 15*x^3 + 113*x^4 + 1105*x^5 + 13219*x^6 + 187103*x^7 + 3058113*x^8 + 56675297*x^9 + 1174295267*x^10 + ...

such that

A(x) = 1 + x + x*tan(3*arctan(x)) + x*tan(3*arctan(x))*tan(5*arctan(x)) + x*tan(3*arctan(x))*tan(5*arctan(x))*tan(7*arctan(x)) + x*tan(3*arctan(x))*tan(5*arctan(x))*tan(7*arctan(x))*tan(9*arctan(x)) + ...

PROG

(PARI) {a(n)=local(X=x+x*O(x^n), Gf); Gf=sum(m=0, n, prod(k=1, m, tan((2*k-1)*atan(X)))); polcoeff(Gf, n)}

for(n=0, 30, print1(a(n), ", "))

CROSSREFS

Cf. A177381, A295759.

Sequence in context: A299308 A300109 A056053 * A059849 A123853 A166885

Adjacent sequences:  A295755 A295756 A295757 * A295759 A295760 A295761

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jan 28 2018

STATUS

approved

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Last modified April 5 06:13 EDT 2020. Contains 333238 sequences. (Running on oeis4.)