OFFSET
1,2
COMMENTS
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..5000
MATHEMATICA
DivisorSigma[1, Select[Accumulate[Range[200]]/3, IntegerQ]] (* G. C. Greubel, Jun 06 2017 *)
PROG
(Scheme)
;; This uses memoization-macro definec:
;; Antti Karttunen, Dec 20 2015
(PARI) a(n) = sigma((3*n^2 + 2*n + (n%2) * (2*n + 1)) / 8); \\ Michel Marcus, Dec 21 2015
(Magma) [DivisorSigma(1, (3*n^2+2*n+(n mod 2)*(2*n+1)) div 8): n in [1..70]]; // Vincenzo Librandi, Dec 21 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Nov 24 2015
STATUS
approved