OFFSET
0,2
COMMENTS
From Roberto E. Martinez II, Jan 07 2002: (Start)
Number of edges of the complete tripartite graph of order 7n, K_n,n,5n.
Number of edges of the complete tripartite graph of order 6n, K_n,2n,3n. (End)
11 times the squares. - Omar E. Pol, Dec 13 2008
LINKS
FORMULA
a(n) = 11*A000290(n). - Omar E. Pol, Dec 13 2008
a(n) = 22*n + a(n-1) - 11 (with a(0)=0). - Vincenzo Librandi, Aug 05 2010
From Amiram Eldar, Feb 03 2021: (Start)
Sum_{n>=1} 1/a(n) = Pi^2/66.
Sum_{n>=1} (-1)^(n+1)/a(n) = Pi^2/132.
Product_{n>=1} (1 + 1/a(n)) = sqrt(11)*sinh(Pi/sqrt(11))/Pi.
Product_{n>=1} (1 - 1/a(n)) = sqrt(11)*sin(Pi/sqrt(11))/Pi. (End)
From Elmo R. Oliveira, Nov 29 2024: (Start)
G.f.: 11*x*(1 + x)/(1-x)^3.
E.g.f.: 11*x*(1 + x)*exp(x).
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 2. (End)
EXAMPLE
a(1)=22*1+0-11=11; a(2)=22*2+11-11=44; a(3)=22*3+44-11=99 - Vincenzo Librandi, Aug 05 2010
MATHEMATICA
Table[11*n^2, {n, 0, 35}] (* Amiram Eldar, Feb 03 2021 *)
PROG
(PARI) a(n)=11*n^2 \\ Charles R Greathouse IV, Jun 17 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved