OFFSET
0,3
COMMENTS
Limit a(n)/2^[n*(n-1)/2] = 1.97254925752982255...
EXAMPLE
G.f.: A(x) = 1 + x*B(x)^2; B(x) = 1 + x*C(x)^4; C(x) = 1 + x*D(x)^8;
D(x) = 1 + x*E(x)^16; E(x) = 1 + x*F(x)^32; ...
where the respective sequences begin:
B=[1,1,4,38,724,26385,1837224,247455640,65256486712,...];
C=[1,1,8,156,6008,436870,60346328,16118073852,8445009616488,...];
D=[1,1,16,632,48944,7110684,1956587408,1040720206536,...];
E=[1,1,32,2544,395104,114749560,63023951008,66902165283280,...];
F=[1,1,64,10208,3175104,1843872240,2023417888576,...].
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
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Jul 28 2006
STATUS
approved