A121587 G.f.: A(x) = 1+x*(1+x*(1+x*(...(1+x*(...)^(-n) )...)^-3)^-2)^-1.

1, 1, -1, 3, -14, 87, -672, 6202, -66622, 817205, -11278833, 173092010, -2925096344, 53989582136, -1080876094507, 23331975207984, -540247838958615, 13357882578863941, -351281262266717583, 9790602495326179971, -288289868480192337409, 8942994568771904297378

Offset: 0

Author

Paul D. Hanna, Aug 09 2006

Keywords

• sign

Examples

			G.f.: A(x) = 1 + x/B(x); B(x) = 1 + x/C(x)^2; C(x) = 1 + x/D(x)^3;
D(x) = 1 + x/E(x)^4; E(x) = 1 + x/F(x)^5; ...
where the respective sequences begin:
B=[1,1,-2,9,-58,472,-4584,51481,-655244,9318663,...];
C=[1,1,-3,18,-148,1491,-17496,232556,-3441024,56009937,...];
D=[1,1,-4,30,-300,3605,-49656,763968,-12920820,237676330,...];
E=[1,1,-5,45,-530,7400,-117096,2048865,-39048150,802555995,...];
F=[1,1,-6,63,-854,13587,-242928,4766594,-101163336,...].
		

Crossrefs

Cf. A095793 (variant).

Programs

PARI

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