OFFSET
1,1
COMMENTS
3 is the only number < 10000 whose concatenation of odd primes is prime. Conjecture: Beyond 3 the concatenation of odd primes produce only composite numbers.
MATHEMATICA
Join[{x=3}, Table[First[First/@FactorInteger[x=FromDigits[Flatten[IntegerDigits[{x, Prime[n]}]]]]], {n, 3, 30}]] (* Jayanta Basu, Jun 04 2013 *)
PROG
(PARI) factorconcat(n) = { y=""; forprime(x=3, n, y=concat(Str(y), Str(x)); z=eval(y); a = component(factor(z), 1); print1(a[1]", ") ) }
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Cino Hilliard, Jan 11 2004
EXTENSIONS
Edited and extended by Charles R Greathouse IV, Apr 29 2010
STATUS
approved