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A012670
arctan(tanh(x)*tan(x))=2/2!*x^2-128/6!*x^6+253952/10!*x^10...
1
2, -128, 253952, -2863136768, 107451055603712, -10140668012798148608, 2022780765718183801782272, -757569427466144902069404827648
OFFSET
0,1
FORMULA
(-1)^n * 2^(6n+1) * A090681(n).
CROSSREFS
Sequence in context: A086190 A024345 A012524 * A209248 A153425 A296060
KEYWORD
sign
AUTHOR
Patrick Demichel (patrick.demichel(AT)hp.com)
STATUS
approved