A138210 G.f.: A(x) = 1 + x*(1 + x*(1 + x*(...(1 + x*(...)^(-2n) )...)^-6)^-4)^-2.

1, 1, -2, 11, -96, 1137, -16972, 305653, -6449876, 156135481, -4266372138, 129918213186, -4363433172488, 160251326396727, -6389255111157990, 274851082201092530, -12689236310679318864, 625827924636908620381, -32839089116018960634852

Offset

0,3

Links

Table of n, a(n) for n=0..18.

Example

G.f.: A(x)=1+x/B(x)^2, B(x)=1+x/C(x)^4, C(x)=1+x/D(x)^6, D(x)=1+x/E(x)^8,...
where A(x),B(x),C(x),... are the g.f. of the sequences given below.
A=[1,1,-2,11,-96,1137,-16972,305653,-6449876,156135481,...];
B=[1,1,-4,34,-416,6487,-121740,2660394,-66258116,1852007663,...];
C=[1,1,-6,69,-1088,21126,-480360,12432418,-359714328,11490821943,...];
D=[1,1,-8,116,-2240,52130,-1395592,41877192,-1385795096,50020840015,...];
E=[1,1,-10,175,-4000,108575,-3348372,114475615,-4273407500,...];
F=[1,1,-12,246,-6496,201537,-7039284,270347826,-11252124732,...]; ...

Prog

(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(j=0, n-1, A=1+x*A^(-2*(n-j))); polcoeff(A, n)}

Crossrefs

Cf. A121587, A138212, A138209, A138208.

Sequence in context: A261886 A245895 A231229 * A227465 A295099 A227466

Adjacent sequences: A138207 A138208 A138209 * A138211 A138212 A138213

Keyword

sign

Author

Paul D. Hanna, Mar 06 2008

Status

approved