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A012467 sech(arctan(x)*atan(x))=1-12/4!*x^4+480/6!*x^6-21168/8!*x^8... 1
1, 0, -12, 480, -21168, 741120, 61942848, -29951061504, 8015861467392, -1745546459848704, 215844160641143808, 91751419512905687040, -109687232118939992862720, 71900040403600384794624000 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

CROSSREFS

Sequence in context: A003749 A012395 A012687 * A009083 A012681 A009168

Adjacent sequences:  A012464 A012465 A012466 * A012468 A012469 A012470

KEYWORD

sign

AUTHOR

Patrick Demichel (dml(AT)hpfrcu03.france.hp.com)

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Last modified February 16 18:43 EST 2012. Contains 205939 sequences.