OFFSET
1,4
COMMENTS
Conjecture: a(2) is the only 0 in this sequence.
EXAMPLE
a(33)= 7 as we get primes 331, 337, 3313, 3319, 3323, 3329, 3331, for seven values of k i.e. k = 1, 7, 13, 19, 23, 29, 31. a(20) = 2, the primes are 2011 and 2017 (2003 doesn't count).
MATHEMATICA
d[n_]:=IntegerDigits[n]; Table[c=0; Do[If[PrimeQ[FromDigits[Join[d[n], d[k]]]], c=c+1], {k, n}]; c, {n, 98}] (* Jayanta Basu, May 21 2013 *)
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Mar 03 2002
EXTENSIONS
More terms from Eli McGowan (ejmcgowa(AT)mail.lakeheadu.ca), May 06 2002
Corrected and extended by Jason Earls, Sep 06 2002
STATUS
approved