OFFSET
1,2
COMMENTS
The corresponding composite numbers A002808(a(n)) are 4, 8, 24, 25, 38, 55, 85, ... (see the link for more values).
LINKS
MATHEMATICA
comp = Select[Range[10^6], CompositeQ]; f[n_] := Module[{k = 1}, While[! PrimeQ[k*n + 1], k++]; k]; vs = f /@ comp; m = 0; s = {}; Do[v = vs[[k]]; If[v > m, m = v; AppendTo[s, k]], {k, 1, Length[vs]}]; s
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Jun 05 2022
STATUS
approved