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A067621 Let t = coefficient of x^(2n+1) in expansion of sin(x)/(1-x^2); a(n)=denominator(t)-numerator(t). 0
0, 1, 19, 799, 57527, 6327971, 39486539, 207304329751, 4337444437867, 19284277970756683, 8099396747717806859, 819658950869042054131, 2458976852607126162392999, 1726201750530202565999885299 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Old description: consider the power series of sin(x)/(x+1)=N(0)/D(0)*(x-x^2)+...+N(k)/D(k)*(x^(2k+1)-x^(2k+2))+...; then a(n)=D(n)-N(n).

LINKS

Table of n, a(n) for n=0..13.

FORMULA

a(n) is the difference between denominator and numerator of sum(i=0, n, (-1)^i/(2i+1)!)

MATHEMATICA

Denominator[#]-Numerator[#]&/@Table[Sum[(-1)^i/(2i+1)!, {i, 0, n}], {n, 0, 15}] (* Harvey P. Dale, Apr 18 2012 *)

PROG

(PARI) a(n)=local(t); if(n<0, 0, t=polcoeff(sin(x+O(x^(2*n+2)))/(1-x^2), 2*n+1); denominator(t)-numerator(t)) /* Michael Somos, Feb 01 2004 */

CROSSREFS

Sequence in context: A201708 A280625 A183441 * A206308 A135562 A139194

Adjacent sequences:  A067618 A067619 A067620 * A067622 A067623 A067624

KEYWORD

nonn

AUTHOR

Benoit Cloitre, Feb 02 2002

STATUS

approved

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Last modified November 27 01:16 EST 2021. Contains 349344 sequences. (Running on oeis4.)