OFFSET
0,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 0..10000
EXAMPLE
a(1)= 6160 because sigma(6160)-6160+1 == 11697, sigma(11697)-11697+1 == 6160 and 6160 is the smallest integer for which this holds.
MATHEMATICA
a[n_] := Module[{k = n + 1, s}, While[( s = DivisorSigma[1, k] - k + n) <= k || DivisorSigma[1, s] - s + n != k, k++]; k]; Array[a, 61, 0] (* Amiram Eldar, Dec 24 2020 *)
PROG
(PARI) for(g=0, 60, x=g+1; while(1, a=sigma(x)-x+g; if((a-x)*a, if(sigma(a)-a+g==x, print1(x, ", "); break)); x+=1))
CROSSREFS
KEYWORD
nonn
AUTHOR
Jack Brennen, Jul 06 2004
STATUS
approved