A013478 - OEIS

%I #21 Jul 29 2015 10:21:35

%S 2,242,735842,12696924242,729261623797442,105330801708282667442,

%T 32155390653420235027326242,18430773614710132775756232045842,

%U 18200656974294045189446138614387578242,29009142008847262758691664682458471045155442

%N E.g.f. -arctanh(cos(x)-cosh(x)), coefficients of (4*i+2) only.

%H Matthew House, <a href="/A013478/b013478.txt">Table of n, a(n) for n = 0..112</a>

%F a(n) = (4i+2)! * [x^(4i+2)] -arctanh(cos(x)-cosh(x)).

%p g := taylor(-arctanh(cos(x)-cosh(x)),x=0,100):q := seq((coeff(g,x,4*i+2)*(4*i+2)!),i=0..15);

%o (PARI) my(x = xx + O(xx^60)); v = Vec(serlaplace(-atanh(cos(x)-cosh(x)))); vector(#v\4, i, v[4*i+1]) \\ _Michel Marcus_, Jul 28 2015

%K nonn

%O 0,1

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

%E More terms from _Sascha Kurz_, Mar 24 2002

%E a(0)=2 inserted by _Alois P. Heinz_, Jul 28 2015