OFFSET
1,1
COMMENTS
All terms are = 5 (mod 10).
LINKS
David W. Wilson, Table of n, a(n) for n = 1..10410
EXAMPLE
MATHEMATICA
Select[Flatten@ Table[FromDigits /@ Tuples[{2, 3, 5, 7}, n], {n, 5}], Function[k, Total@ Map[Times @@ # &, Boole@ Map[Total@ Pick[DigitCount@ #, {1, 0, 0, 1, 0, 1, 0, 1, 1, 1}, 1] == 0 &, Transpose@ {#, k/#} &@ Rest@ Take[#, Ceiling[Length[#]/2]] &@ Divisors@ k, {2}]] > 0]] (* Michael De Vlieger, Sep 19 2016 *)
id[n_]:=IntegerDigits[n]; pQ[n_]:=AllTrue[id[n], PrimeQ];
nQ[n_]:=Select[Times@@@Tuples[Select[Divisors[n], AllTrue[id[#], PrimeQ]&], 2], #==n&]
!={};
Select[Flatten@Table[FromDigits/@Tuples[{2, 3, 5, 7}, n], {n, 5}], pQ[#]&&nQ[#]&] (* Ivan N. Ianakiev, Jul 20 2022 *)
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Zak Seidov, Dec 26 2008
STATUS
approved