OFFSET
1,3
COMMENTS
EXAMPLE
a(4) = sigma(a(1) + a(2) + a(3)) = sigma(1+1+3) = sigma(5) = 6.
MATHEMATICA
Module[{lst={1}}, Do[AppendTo[lst, DivisorSigma[1, Total[lst]]], {40}]; lst] (* Harvey P. Dale, Sep 29 2012 *)
PROG
(PARI) print1(1); s=1; for(i=1, 100, k=sigma(s); print1(", "k); s+=k)
CROSSREFS
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Sep 30 2009
EXTENSIONS
Extension and program from Charles R Greathouse IV, Oct 12 2009
STATUS
approved