OFFSET
0,1
COMMENTS
Is a(n) well-defined for all n?
For n > 1, a(n) belongs to sequence A258931.
The terms a(k), for 4 <= k <= 100, if they exist, are larger than 3*10^10. - Giovanni Resta, Jun 15 2015
EXAMPLE
For n=2, sigma(x)=124 for x=48 and 75, and 48+75 = 123 < 124.
For n=3, sigma(x)=10714158 for x=3031200, 3417300, and 3987450; and their sum is 10435950 (<10714158).
PROG
(PARI) a(n)=x=0; while(x++, u=List(); for(i=1, x, if(sigma(i)==x, listput(u, i))); if(#u==n&vecsum(Vec(u))<x, return(x))) \\ not optimized because the same sigma values are calculated over and over again instead of being kept
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jeppe Stig Nielsen, Jun 15 2015
STATUS
approved