OFFSET
0,1
COMMENTS
Also 1/3-1/5-1/7+1/9+1/11-1/13-1/15+1/17+1/19--++... = Pi*sqrt(2)/4-1 - Miklos Kristof, Sep 15 2008
Also sum(2*(-1)^n/((4*n+3)*(4*n+5)), n=0..infinity) = Pi*sqrt(2)/4-1 - Miklos Kristof, Sep 15 2008
LINKS
Index entries for linear recurrences with constant coefficients, signature (5,-10,10,-5,1).
FORMULA
G.f.: 3*(315 + 10580*x + 18850*x^2 + 3028*x^3 - 5*x^4)/(1-x)^5.
E.g.f: (945 + 35520*x + 78720*x^2 + 36864*x^3 + 4096*x^4)*exp(x).
a(n) = 5*a(n-1)-10*a(n-2)+10*a(n-3)-5*a(n-4)+a(n-5). - Wesley Ivan Hurt, Apr 26 2021
MAPLE
seq((8*n+3)*(8*n+5)*(8*n+7)*(8*n+9), n=0..30);
sum(32*(4*n+3)/((8*n+3)*(8*n+5)*(8*n+7)*(8*n+9)), n=0..infinity) = Pi*sqrt(2)/4-1. Maple: evalf(Pi*sqrt(2)/4-1, 30); gives 0.11072073453959156175397024752... - Miklos Kristof, Sep 15 2008
MATHEMATICA
Times@@@(#+{3, 5, 7, 9}&/@(8Range[0, 25])) (* Harvey P. Dale, Mar 14 2011 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Miklos Kristof, Jan 06 2008, Sep 15 2008
STATUS
approved