OFFSET
0,2
COMMENTS
See A124869 for comments and references.
FORMULA
a(n) = denominator(Re(1/(-1 + i*3)^n) ).
Conjectures from Colin Barker, Jul 16 2019: (Start)
G.f.: (1 + 10*x + 25*x^2 + 500*x^3 - 31250*x^6) / ((1 - 50*x^2)*(1 + 50*x^2)).
a(n) = 2500*a(n-4) for n>6.
(End)
EXAMPLE
a(0) = 1 = denominator of Re((-1+3*i)^0) = 1/1 + 0*i.
a(1) = 10 = denominator of Re(1/(-1+3*i)) = -1/10 - i*3/10.
a(2) = 25 = denominator of Re((-1+3*i)^(-2)) = -2/25 + i*3/50.
a(3) = 500 = denominator of Re((-1+3*i)^(-3)) = 13/500 + i*9/500.
a(4) = 2500 = denominator of Re((-1+3*i)^(-4)) = 7/2500 - i*6/625.
a(5) = 25000 = denominator of Re((-1+3*i)^(-5)) = -79/25000 + i*3/25000.
a(6) = 31250 = denominator of Re((-1+3*i)^(-6)) = 11/31250 + i*117/125000.
CROSSREFS
KEYWORD
easy,frac,nonn
AUTHOR
Jonathan Vos Post, Nov 11 2006
EXTENSIONS
Removed square roots from definition and formula. - R. J. Mathar, May 02 2009
STATUS
approved