OFFSET
0,3
EXAMPLE
A = 1 + x*A + x^2*A^2 + x^3*A^4 + x^4*A^8 + x^5*A^16 +...
= 1 + (x + x^2 + 2*x^3 + 5*x^4 + 15*x^5 + 52*x^6 +...)
+ (x^2 + 2*x^3 + 5*x^4 + 14*x^5 + 44*x^6 + 154*x^7 +...)
+ (x^3 + 4*x^4 + 14*x^5 + 48*x^6 + 169*x^7 +...)
+ (x^4 + 8*x^5 + 44*x^6 + 208*x^7 +...)
+ (x^5 + 16*x^6 + 152*x^7 +...) +...
PROG
(PARI) {a(n)=local(A=1+x+x*O(x^n)); for(k=1, n, A=1+sum(j=1, n, x^j*A^(2^(j-1)))); polcoeff(A, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 17 2005
STATUS
approved