OFFSET
0,3
LINKS
T. D. Noe, Table of n, a(n) for n=0..100
MAPLE
MATHEMATICA
a[0] = a[1] = 1; a[n_] := a[n] = DivisorSigma[1, a[n-1]] + DivisorSigma[1, a[n-2]]; Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Feb 08 2016 *)
nxt[{a_, b_}]:={b, DivisorSigma[1, a]+DivisorSigma[1, b]}; NestList[nxt, {1, 1}, 30][[All, 1]] (* Harvey P. Dale, Dec 09 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved