OFFSET
0,3
COMMENTS
Conjectures: (Start)
a(n) == 1 (mod 5) for n>=0;
a(n) == 0 (mod 17) for n>=16;
a(n) == 0 (mod 19) for n>=17;
a(n) == 0 (mod 37) for n>=36.
(End)
FORMULA
E.g.f.: 1/(1 - 5*Series_Reversion( Integral (1 - 25*x^2)^(1/5) dx ))^(1/5).
EXAMPLE
E.g.f.: A(x) = 1 + x + 6*x^2/2! + 76*x^3/3! + 1296*x^4/4! + 30976*x^5/5! +...
Related series.
A(x)^7 = 1 + 7*x + 84*x^2/2! + 1498*x^3/3! + 34776*x^4/4! + 1006432*x^5/5! +...
Note that 1 - 1/A(x)^5 is an odd function:
1 - 1/A(x)^5 = 5*x + 50*x^3/3! + 11000*x^5/5! + 7460000*x^7/7! + 10335200000*x^9/9! +...
where Series_Reversion((1 - 1/A(x)^5)/5) = Integral (1-25*x^2)^(1/5) dx.
PROG
(PARI) {a(n)=local(A=1); for(i=0, n, A=1+intformal(A^7*subst(A, x, -x) +x*O(x^n) )); n!*polcoeff(A, n)}
for(n=0, 20, print1(a(n), ", "))
(PARI) {a(n)=local(A=1); A=1/(1-5*serreverse(intformal((1-25*x^2 +x*O(x^n))^(1/5))))^(1/5); n!*polcoeff(A, n)}
for(n=0, 20, print1(a(n), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Apr 08 2014
STATUS
approved