OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..5000
B. A. Huberman and T. Hogg, Complexity and adaptation, Evolution, games and learning (Los Alamos, N.M., 1985). Phys. D 22 (1986), no. 1-3, 376-384.
Index entries for linear recurrences with constant coefficients, signature (5, -10, 10, -5, 1).
FORMULA
Expansion of x*(1+2x+2x^2)/(1-x)^5.
a(n) = n*(n+1)*(5*n^2+n+6)/24. - T. D. Noe, Feb 09 2007
a(1)=1, a(2)=7, a(3)=27, a(4)=75, a(5)=170, a(n)=5*a(n-1)- 10*a(n-2)+ 10*a(n-3)-5*a(n-4)+a(n-5). - Harvey P. Dale, Jul 20 2011
EXAMPLE
a(7) = 7*28 - (7*0+4*1+1*3-2*6-5*10-8*15-11*21) = 602. - Bruno Berselli, Jun 22 2013
MATHEMATICA
Table[n(n+1)(5n^2+n+6)/24, {n, 40}] (* or *) LinearRecurrence[ {5, -10, 10, -5, 1}, {1, 7, 27, 75, 170}, 40] (* Harvey P. Dale, Jul 20 2011 *)
PROG
(Magma) [n*(n+1)*(5*n^2+n+6)/24: n in [1..45]]; // Vincenzo Librandi, Jul 21 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved