A158120 Unsigned bisection of A157304 and A157305.

1, 2, 26, 1378, 141202, 22716418, 5218302090, 1619288968386, 653379470919714, 333014944014777730, 209463165121436380282, 159492000935562428176162, 144654795258284936534929586, 154140229756873813307283828098

Offset

0,2

Links

Paul D. Hanna, Table of n, a(n) for n=0..50

Example

G.f.: A(x) = 1 + 2*x + 26*x^2 + 1378*x^3 + 141202*x^4 +...
RELATED FUNCTIONS.
G.f. of A157305, B(x) = x + A(-x^2), satisfies the condition
that both B(x) and F(x) = B(x*F(x)^2) = o.g.f. of A157307
have zeros for every other coefficient after initial terms:
A157305 = [1,1,-2,0,26,0,-1378,0,141202,0,-22716418,0,...];
A157307 = [1,1,0,-7,0,242,0,-17771,0,2189294,0,-404590470,0,...].
...
G.f. of A157304, C(x) = 2+x - A(-x^2), satisfies the condition
that both C(x) and G(x) = C(x/G(x)^2) = o.g.f. of A157302
have zeros for every other coefficient after initial terms:
A157308 = [1,1,2,0,-26,0,1378,0,-141202,0,22716418,0,...];
A157302 = [1,1,0,-5,0,183,0,-14352,0,1857199,0,-355082433,0,...].
...

Prog

(PARI) {a(n)=local(A=[1, 1]); for(i=1, 2*n, if(#A%2==0, A=concat(A, t); A[ #A]=-subst(Vec(serreverse(x/Ser(A)))[ #A], t, 0)); if(#A%2==1, A=concat(A, t); A[ #A]=-subst(Vec(x/serreverse(x*Ser(A)))[ #A], t, 0))); (-1)^n*Vec(x/serreverse(x*Ser(A)))[2*n+1]}

Crossrefs

Cf. A157304, A157305, A157302, A157307, A158119.

Sequence in context: A002704 A015215 A363892 * A209916 A337578 A156213

Adjacent sequences: A158117 A158118 A158119 * A158121 A158122 A158123

Keyword

nonn

Author

Paul D. Hanna, Mar 12 2009

Status

approved