OFFSET
1,2
COMMENTS
Conjecture: sequence is injective (all terms of this sequence occur only once).
The conjecture is true for the first 100000 terms. - Harvey P. Dale, Dec 02 2017
LINKS
Jaroslav Krizek, Table of n, a(n) for n = 1..100
FORMULA
a(p) = p + 1 for prime p.
EXAMPLE
The divisors of 6 are 1, 2, 3, 6. a(n) = 1 + (1*2) + (1*2*3) + (1*2*3*6) = 1 + 2 + 6 + 36 = 45.
MATHEMATICA
f[x_]:=Module[{d=Divisors[x]}, Total[Table[Times@@Take[d, n], {n, Length[ d]}]]]; Array[f, 50] (* Harvey P. Dale, Dec 02 2017 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jaroslav Krizek, Dec 22 2012
STATUS
approved