OFFSET
0,4
COMMENTS
The denominators are given in A128501.
The limit n -> infinity of the rationals r(n) defined below is Pi/(3*sqrt(3)).
LINKS
FORMULA
a(n)=numerator(r(n)) with the rationals r(n):=Sum_{k=0..n} ((-1)^k)*S(k,1)/(k+1) with Chebyshev's S-Polynomials S(k,1)=[1,1,0,-1,-1,0] periodic sequence with period 6. See A010892.
EXAMPLE
Rationals: [1, 1/2, 1/2, 3/4, 11/20, 11/20, 97/140, 159/280, 159/280, 187/280,...]
Pi/(3*sqrt(3))=+1/1 -1/2 +1/4 -1/5 +1/7 -1/8 +1/10 -1/11 +1/13 -+
CROSSREFS
KEYWORD
nonn,frac,easy
AUTHOR
Wolfdieter Lang Apr 04 2007
STATUS
approved