OFFSET
0,2
EXAMPLE
G.f.: A(x) = 1 + 2*x + 9*x^2 + 59*x^3 + 462*x^4 + 4011*x^5 + 37253*x^6 +...
where the g.f. A = A(x) satisfies the equivalent expressions:
A = 1 + x*A*(1-A^2)/(1-A) + x^2*A^3*(1-A^3)/(1-A) + x^3*A^6*(1-A^4)/(1-A) + x^4*A^10*(1-A^5)/(1-A) + x^5*A^15*(1-A^6)/(1-A) +...
A = 1 + x*(A + A^2) + x^2*(A^3 + A^4 + A^5) + x^3*(A^6 + A^7 + A^8 + A^9) + x^4*(A^10 + A^11 + A^12 + A^13 + A^14) +...
PROG
(PARI) {a(n)=local(A=1+x); for(i=1, n, A=sum(m=0, n, x^m*A^(m*(m+1)/2)*sum(k=0, m, A^k)+x*O(x^n))); polcoeff(A, n)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Nov 07 2011
STATUS
approved