OFFSET
1,2
COMMENTS
EXAMPLE
a(6) = 6 + d(a(5)) = 6 + d(9) = 6 + 3 = 9.
MATHEMATICA
a[1]=1; a[n_]:=a[n]=n+DivisorSigma[0, a[n-1]]; Array[a, 50] (* Amiram Eldar, Nov 21 2018 *)
PROG
(PARI) seq(n)={my(v=vector(n)); v[1]=1; for(n=2, #v, v[n]=n + numdiv(v[n-1])); v} \\ Andrew Howroyd, Nov 20 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Todor Szimeonov, Nov 20 2018
STATUS
approved