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A168404 E.g.f.: Sum_{n>=0} tan(2^n*x)^n/n!. 2
1, 2, 16, 528, 67584, 34210304, 69391122432, 565356426987520, 18478277930015260672, 2419401354886413876592640, 1267940756758206239694099841024, 2658665157828553829995392867121496064 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..11.

FORMULA

a(n) = [x^n/n! ] exp(2^n*tan(x)) for n>=0.

EXAMPLE

E.g.f.: A(x) = 1 + 2*x + 16*x^2/2! + 528*x^3/3! + 67584*x^4/4! +...

A(x) = 1 + tan(2*x) + tan(4*x)^2/2! + tan(8*x)^3/3! + tan(16*x)^4/4! +...+ tan(2^n*x)^n/n! +...

a(n) = coefficient of x^n/n! in G(x)^(2^n) where G(x) = exp(tan(x)):

G(x) = 1 + x + x^2/2! + 3*x^3/3! + 9*x^4/4! + 37*x^5/5! + 177*x^6/6! +...+ A006229(n)*x^n/n! +...

PROG

(PARI) {a(n)=n!*polcoeff(sum(k=0, n, tan(2^k*x +x*O(x^n))^k/k!), n)}

(PARI) {a(n)=n!*polcoeff(exp(2^n*tan(x +x*O(x^n))), n)}

CROSSREFS

Cf. A006229 (exp(tan x)), variants: A136632, A168402, A168403, A168405, A168406, A168407, A168408.

Sequence in context: A168405 A012919 A012914 * A013087 A121271 A013136

Adjacent sequences:  A168401 A168402 A168403 * A168405 A168406 A168407

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Nov 25 2009

STATUS

approved

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Last modified January 24 10:24 EST 2020. Contains 331193 sequences. (Running on oeis4.)