A121588 G.f.: A(x) = 1+x*(1+x*(1+x*(...(1+x*(...)^(-2^n) )...)^-4)^-2)^-1.

1, 1, -1, 3, -16, 145, -2347, 72498, -4459887, 554300965, -139235329270, 70475747813447, -71685052573258824, 146249172542467865074, -597744865134782025119044, 4890851047359454263328433041, -80078758027845307168595201926254

Offset

0,4

Comments

Limit |a(n)|/2^[(n-1)*(n-2)/2] = 1.97254925752982255...

Links

Table of n, a(n) for n=0..16.

Example

G.f.: A(x) = 1 + x/B(x); B(x) = 1 + x/C(x)^2; C(x) = 1 + x/D(x)^4;
D(x) = 1 + x/E(x)^8; E(x) = 1 + x/F(x)^16; ...
where the respective sequences begin:
B=[1,1,-2,11,-112,2025,-67324,4305909,-545113744,...];
C=[1,1,-4,42,-836,30259,-2041616,265712044,-68214603840,...];
D=[1,1,-8,164,-6456,467850,-63614840,16702037652,...];
E=[1,1,-16,648,-50736,7358500,-2008876560,1059405119352,...];
F=[1,1,-32,2576,-402272,116732040,-63860549280,...].

Prog

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

Crossrefs

Cf. A120959 (variant).

Sequence in context: A109398 A294003 A006058 * A331538 A306397 A264660

Adjacent sequences: A121585 A121586 A121587 * A121589 A121590 A121591

Keyword

sign

Author

Paul D. Hanna, Aug 09 2006

Status

approved