OFFSET
0,2
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..5000
FORMULA
a(n) = 4*numerator(n^2/(n^2 + 3*n + 3)).
Sum_{n>=1} 1/a(n) = 11*Pi^2/216. - Amiram Eldar, Aug 14 2022
G.f.: 4*x*(1 + 4*x + 3*x^2 + 13*x^3 + 13*x^4 + 3*x^5 + 4*x^6 + x^7)/(1-x^3)^3. - G. C. Greubel, Oct 27 2022
MAPLE
A046162 := proc(n) (n-1)^2/(n^2+n+1) ; numer(%) ; end proc: A147560 := proc(n) 4*A046162(n+1) ; end proc: seq(A147560(n), n=0..70) ; # R. J. Mathar, Dec 15 2009
MATHEMATICA
a[n_] := 4 * Numerator[n^2/(n^2 + 3*n + 3)]; Array[a, 50, 0] (* Amiram Eldar, Aug 14 2022 *)
PROG
(Magma) [4*Numerator(n^2/(n^2+3*n+3)): n in [0..70]]; // G. C. Greubel, Oct 27 2022
(SageMath) [4*numerator(n^2/(n^2 +3*n +3)) for n in range(71)] # G. C. Greubel, Oct 27 2022
CROSSREFS
KEYWORD
nonn,easy,less
AUTHOR
Paul Curtz, Nov 07 2008
EXTENSIONS
More terms from R. J. Mathar, Dec 15 2009
STATUS
approved