OFFSET
1,2
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ n log n. - Charles R Greathouse IV, Dec 27 2013
EXAMPLE
a(21) = 21 + (2)(1) = 23 (prime). a(67) = 67 + (6)(7) = 109 (prime). a(169) = 169 + (1)(6)(9) = 223 (prime).
MATHEMATICA
fQ[n_] := PrimeQ[n + Times @@ IntegerDigits@n]; Select[ Range@1000, fQ@# &] (* Robert G. Wilson v, May 04 2009 *)
PROG
(PARI) dprod(n)=n=digits(n); prod(i=1, #n, n[i])
is(n)=isprime(dprod(n)+n) \\ Charles R Greathouse IV, Dec 27 2013
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Kyle D. Balliet, Mar 04 2009
EXTENSIONS
More terms from Robert G. Wilson v, May 04 2009
STATUS
approved