OFFSET
1,1
COMMENTS
Erdos conjectures that this sequence is finite.
LINKS
Robert Israel, Table of n, a(n) for n = 1..100 (terms 1..98 from Michel Marcus)(all terms <= 10^8).
Paul Erdos, Some unconventional problems in number theory, Acta Mathematica Hungarica, 33(1):71-80, 1979. See p. 73.
MAPLE
N:= 10^6: # to get all terms <= N
Res:= 6: v:= 6:
for n from 7 to N do
if not isprime(n-1) then v:= max(v, n-1 + min(numtheory:-factorset(n-1))) fi;
if v <= n then Res:= Res, n fi;
od:
Res; # Robert Israel, Dec 03 2018
MATHEMATICA
f[n_] := Module[{smax = 0}, Do[If[CompositeQ[m], smax = Max[smax, m + FactorInteger[m][[1, 1]]]], {m, 2, n-1}]; smax]; aQ[n_] := f[n]<=n; Select[Range[6, 1000], aQ] (* Amiram Eldar, Dec 02 2018 *)
PROG
(PARI) f(n) = {my(smax = 0); forcomposite(m=1, n-1, smax = max(smax, m + factor(m)[1, 1]); ); smax; } \\ A322292
isok(n) = f(n) <= n;
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Michel Marcus, Dec 02 2018
STATUS
approved