OFFSET
1,1
EXAMPLE
322 is here since for 322 additive digital root is 7 and multiplicative digital root is 2, both are primes.
MATHEMATICA
a[n_] := NestWhile[Times@@IntegerDigits[#]&, n, #>9&]; Select[Range[1700], !PrimeQ[#] && And@@PrimeQ[{a[#], Mod[#, 9]}]&]
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Jayanta Basu, Jun 03 2013
STATUS
approved