OFFSET
1,1
COMMENTS
a(4) > 10^10.
MATHEMATICA
s[n_] := DivisorSum[n, # &, #^2 > n && CoprimeQ[#, n/#] &]; Select[Range[1.5*10^7], s[#] == s[# + 1] &]
CROSSREFS
KEYWORD
nonn,bref,more
AUTHOR
Amiram Eldar, Apr 12 2020
STATUS
approved