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A012350 sec(arcsin(x)*arcsin(x))=1+12/4!*x^4+240/6!*x^6+17808/8!*x^8... 0
1, 0, 12, 240, 17808, 1637760, 242818752, 48180857088, 12774673068288, 4307001787772928, 1807577755864845312, 922535092598044569600, 562968743814613569146880, 404689929495830909079552000 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

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

FORMULA

a(n) ~ 2 * cos(sqrt(Pi/2)) * (2*n)! / (sqrt(2*Pi) * sin(sqrt(Pi/2))^(2*n+1)). - Vaclav Kotesovec, Feb 08 2015

MATHEMATICA

nn = 20; Table[(CoefficientList[Series[Sec[ArcSin[x]^2], {x, 0, 2*nn}], x] * Range[0, 2*nn]!)[[n]], {n, 1, 2*nn+1, 2}] (* Vaclav Kotesovec, Feb 08 2015 *)

CROSSREFS

Sequence in context: A012349 A012302 A012543 * A220216 A126687 A064749

Adjacent sequences:  A012347 A012348 A012349 * A012351 A012352 A012353

KEYWORD

nonn

AUTHOR

Patrick Demichel (patrick.demichel(AT)hp.com)

STATUS

approved

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Last modified February 22 23:03 EST 2019. Contains 320411 sequences. (Running on oeis4.)