OFFSET
1,3
FORMULA
G.f.: (1+x^2-sqrt(1-2*x^2-8*x^3+x^4))/2. - Michael Somos, Jun 08 2000
Conjecture: n*(n^2+n+1)*a(n) +(n-1)*(n^2+2*n+3)*a(n-1) -2*(n-3)*(n^2+n+1)*a(n-2) +2*(-5*n^3+16*n^2+19*n+30)*a(n-3) +(-7*n^3+23*n^2+59*n+126)*a(n-4) +(n-7)*(n^2+2*n+3)*a(n-5)=0. - R. J. Mathar, Feb 25 2015
PROG
(PARI) a(n)=polcoeff((x^2-sqrt(1-2*x^2-8*x^3+x^4+x*O(x^n)))/2, n)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved