OFFSET
0,1
LINKS
T. D. Noe, Table of n, a(n) for n = 0..200
Index entries for linear recurrences with constant coefficients, signature (42,-609,3948,-12180,16800,-8000).
FORMULA
a(n) = (1 + 2^n + 4^n)*(1 + 5^n). - Bruno Berselli, Apr 17 2014
G.f.: -6*(2800*x^5 -4060*x^4 +1974*x^3 -406*x^2 +35*x -1) / ((x -1)*(2*x -1)*(4*x -1)*(5*x -1)*(10*x -1)*(20*x -1)). - Colin Barker, Apr 20 2014
MATHEMATICA
Total[#^Range[0, 20]&/@Divisors[20]] (* Vincenzo Librandi, Apr 17 2014 *)
Table[(1 + 2^n + 4^n) (1 + 5^n), {n, 0, 20}] (* Bruno Berselli, Apr 17 2014 *)
PROG
(Sage) [sigma(20, n) for n in range(0, 16)] # Zerinvary Lajos, Jun 04 2009
(Magma) [DivisorSigma(n, 20): n in [0..20]]; // Vincenzo Librandi, Apr 17 2014
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved