OFFSET
1,3
FORMULA
Self-convolution yields A212392.
EXAMPLE
G.f.: A(x) = x + x^4 + 4*x^7 + 24*x^10 + 168*x^13 + 1284*x^16 + 10384*x^19 +...
such that
A(A(x)^2)^2 = x^4 + 4*x^7 + 24*x^10 + 168*x^13 + 1284*x^16 + 10384*x^19 +...
where
A(x)^2 = x^2 + 2*x^5 + 9*x^8 + 56*x^11 + 400*x^14 + 3096*x^17 + 25256*x^20 +...+ A212392(n)*x^(3*n-1) +...
PROG
(PARI) {a(n)=local(A=x+x^4); for(i=1, n, A=x+subst(A^2, x, A^2+O(x^(3*n)))); polcoeff(A, 3*n-2)}
for(n=1, 30, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 13 2012
STATUS
approved