OFFSET
1,2
COMMENTS
Equals row sums of triangle A160182. - Gary W. Adamson, May 03 2009
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
G.f. A(x) satisfies: A(x) = x * (1 + x / (1 - x) + A(x) + A(x^2) + A(x^3) + ...). - Ilya Gutkovskiy, Jun 09 2021
EXAMPLE
a(7) = 1 + a(1) + a(2) + a(3) + a(6) = 1 + 1 + 2 + 4 + 12 = 20.
MATHEMATICA
a[1] = 1; a[n_] := a[n] = 1 + Sum[a[k], {k, Divisors[n-1]}]; Table[ a[n], {n, 1, 51}] (* Jean-François Alcover, Dec 20 2011 *)
PROG
(Haskell)
a068336 n = a068336_list !! (n-1)
a068336_list = 1 : f 1 where
f x = (1 + sum (map a068336 $ a027750_row x)) : f (x + 1)
-- Reinhard Zumkeller, Dec 20 2014
(PARI) a(n) = if (n==1, 1, 1+ sumdiv(n-1, d, a(d))); \\ Michel Marcus, Oct 30 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
Leroy Quet, Feb 27 2002
STATUS
approved