OFFSET
1,2
LINKS
Metin Sariyar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from Harry J. Smith)
MAPLE
with(numtheory): seq( `if`(n=1, 0, sigma(n^2 -1)), n=1..100); # G. C. Greubel, Dec 31 2019
MATHEMATICA
Table[If[n==1, 0, DivisorSigma[1, n^2 - 1]], {n, 120}] (* corrected by Metin Sariyar, Dec 12 2019 *)
PROG
(PARI) a(n)={if(n<2, 0, sigma(n^2 - 1))}
(Magma) [0] cat [DivisorSigma(1, n^2 -1): n in [2..100]]; // G. C. Greubel, Dec 31 2019
(Sage) [0]+[sigma(n^2 -1, 1) for n in (2..100)] # G. C. Greubel, Dec 31 2019
(GAP) Concatenation([0], List([2..100], n-> Sigma(n^2 -1) )); # G. C. Greubel, Dec 31 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Jason Earls, Jul 21 2001
EXTENSIONS
Name corrected by Omar E. Pol, Dec 08 2019
STATUS
approved