OFFSET
1,1
COMMENTS
First differences in A010696.
LINKS
FORMULA
a(n) = 8*n - a(n-1) - 10, with a(1)=2. - Vincenzo Librandi, Aug 06 2010
From Bruno Berselli, May 11 2011: (Start)
G.f.: 2*x*(1+x+2*x^2)/((1+x)*(1-x)^2).
a(n) = 4*n-(-1)^n-3.
Sum_{i=1..n} a(i) = 2*A014848(n).
a(n) = 2*A042963(n-1). (End)
Sum_{n>=1} (-1)^(n+1)/a(n) = Pi/16 + log(2)/8. - Amiram Eldar, Dec 18 2021
MATHEMATICA
Select[Range[250], MemberQ[{2, 4}, Mod[#, 8]] &] (* Amiram Eldar, Dec 18 2021 *)
PROG
(Magma) [ n: n in [2..234 by 2] | n mod 8 in [2, 4] ]; // Bruno Berselli, May 11 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Vincenzo Librandi, Aug 06 2010
STATUS
approved