OFFSET
0,3
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..9000
Vaclav Kotesovec, Graph a(n+1)/a(n)
FORMULA
1 <= a(n+1)/a(n) <= 2. - Vaclav Kotesovec, Oct 14 2018
By empirical observation a(n) ~ 3.179662855437*exp(0.3175*n). - Ctibor O. Zizka, Oct 15 2018
EXAMPLE
a(4) = a(3)+a(1) = a(2)+a(1)+a(1) = a(1)+a(0)+a(1)+a(1) = 4.
MATHEMATICA
a[n_] := a[n] = If[n < 2, 1, a[n-1] + a[n - DivisorSigma[0, n]]]; Table[a[n], {n, 0, 50}] (* Vaclav Kotesovec, Oct 14 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Ctibor O. Zizka, Oct 11 2018
STATUS
approved