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A242240 Expansion of Jacobi sn(x, 1/2) / cd(x, 1/2). 2
0, 1, 0, 0, 0, 12, 0, 0, 0, 3024, 0, 0, 0, 4390848, 0, 0, 0, 21224560896, 0, 0, 0, 257991277243392, 0, 0, 0, 6628234834692624384, 0, 0, 0, 319729080846260095008768, 0, 0, 0, 26571747463798134334265819136, 0, 0, 0, 3564202847752289659513902717468672, 0, 0, 0 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,6

LINKS

Table of n, a(n) for n=0..40.

FORMULA

a(n) = |A104203(n)|.

E.g.f.: sn(x, 1/2) / cd(x, 1/2).

E.g.f. A(x) satisfies A(x)^2 = sinh(2 * Integral A(x) dx). - Michael Somos, Jun 17 2017

EXAMPLE

G.f. = x + 12*x^5 + 3024*x^9 + 4390848*x^13 + 21224560896*x^17 + ...

MATHEMATICA

a[ n_] := If[ n<0, 0, n! SeriesCoefficient[ JacobiSN[x, 1/2] / JacobiCD[x, 1/2], {x, 0, n}]];

PROG

(PARI) {a(n) = if( n<0, 0, n! * polcoeff( serreverse( intformal( (1 + x^4 + x * O(x^n))^(-1/2))), n))};

CROSSREFS

Cf. A104203.

Sequence in context: A200512 A280832 A104203 * A225341 A004012 A270256

Adjacent sequences:  A242237 A242238 A242239 * A242241 A242242 A242243

KEYWORD

nonn

AUTHOR

Michael Somos, May 09 2014

STATUS

approved

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Last modified February 21 06:40 EST 2019. Contains 320371 sequences. (Running on oeis4.)