OFFSET
1,2
LINKS
T. D. Noe, Table of n, a(n) for n = 1..1000
F. Russo, A set of new Smarandache functions, sequences and conjectures in number theory, American Research Press 2000 .
EXAMPLE
a(1)=1 since 1 has 1 divisor; a(3)=2 since 1 has 1 divisor, 2 has 2 divisors and 1+2=3; a(2)=4 since 1+2+2+3=8, a multiple of 4, while 1, 1+2 and 1+2+2 are not multiples of 4.
MATHEMATICA
a[n_] := (m = 1; While[ !Divisible[ Sum[ DivisorSigma[0, k], {k, 1, m}], n], m++]; m); Table[ a[n], {n, 1, 69}] (* Jean-François Alcover, Dec 28 2011 *)
Module[{nn=300, d}, d=Accumulate[DivisorSigma[0, Range[nn]]]; Table[ SelectFirst[ Thread[{d, Range[nn]}], Divisible[#[[1]], n]&], {n, 70}]][[All, 2]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 20 2020 *)
CROSSREFS
KEYWORD
easy,nice,nonn
AUTHOR
Felice Russo, Feb 25 2000
EXTENSIONS
More terms from Matthew M. Conroy, May 13 2001
STATUS
approved