OFFSET
1,2
COMMENTS
Numbers such that A243970(n) = n.
Is this sequence infinite? - Franklin T. Adams-Watters, Jul 20 2017
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
EXAMPLE
From n=1 to 4, these partial sums are: 1; 2, 3; 3, 4; 4, 6, 7. So it is not possible to obtain 5 with any partial sum of divisors of numbers that are less than 5. And indeed A243970(5) is equal to 5. Hence 5 is in this sequence.
MATHEMATICA
Module[{nn = 432, s}, s = Array[Function[d, Array[Total@ Take[d, -#] &, Length@ d]]@ Divisors@ # &, nn - 1]; Select[Range@ nn, ! MemberQ[Flatten@ Take[s, # - 1], #] &]] (* Michael De Vlieger, Jul 22 2017 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, Jun 16 2014
STATUS
approved