OFFSET
0,3
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..500
FORMULA
G.f. satisfies: A(x) = 1 + x*(1 - x*A(x)^6)^6.
G.f. satisfies: [A(x)^7 + A(-x)^7]/2 = [A(x)^6 + A(-x)^6]/2.
EXAMPLE
A(x) = 1 + x - 6*x^2 - 21*x^3 + 286*x^4 + 1281*x^5 - 20592*x^6 -++-...
A(x)^6 = 1 + 6*x - 21*x^2 - 286*x^3 + 1281*x^4 + 20592*x^5 - 100226*x^6 -...
A(x)^7 = 1 + 7*x - 21*x^2 - 364*x^3 + 1281*x^4 + 27027*x^5 - 100226*x^6 -...
Note that a bisection of A^7 equals a bisection of A^6.
PROG
(PARI) a(n)=local(A=x+x*O(x^n)); for(i=0, n, A=1+x*subst(A, x, -x)^6); polcoeff(A, n)
CROSSREFS
KEYWORD
sign
AUTHOR
Paul D. Hanna, Jul 19 2008
STATUS
approved