OFFSET
1,1
COMMENTS
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..4725 (terms whose lesser counterparts below 2*10^11)
David Moews, Perfect, amicable and sociable numbers.
MATHEMATICA
f[p_, e_] := DivisorSum[e+1, p^(#-1)&]; mesigma[1]=1; mesigma[n_] := Times @@ f @@@FactorInteger@ n; s={}; mes[n_] := mesigma[n]-n; Do[m=mes[n]; If[m>n && mes[m]==n, AppendTo[s, m]], {n, 1, 10000}]; s
PROG
(PARI) f(n) = {my(f=factor(n)); prod(i=1, #f[, 1], sumdiv(f[i, 2]+1, d, f[i, 1]^(d-1))); } \\ A241405
fm(n) = f(n) - n;
isok(n) = my(fn=fm(n)); (fn > 0) && (fn < n) && (fm(fn) == n); \\ Michel Marcus, Jan 30 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Jan 26 2019
STATUS
approved