OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
Concatenation of composite 4 and fourth prime 7 is the prime 47, hence 4 is in the sequence. Concatenation of composite 36 and 36th prime 151 is the prime 36151, hence 36 is in the sequence.
MATHEMATICA
concatQ[n_]:=PrimeQ[FromDigits[Join[IntegerDigits[n], IntegerDigits[ Prime[n]]]]]; nn=400; Select[Complement[Range[nn], Prime[Range[ PrimePi[nn]]]], concatQ] (* Harvey P. Dale, Jun 05 2011 *)
PROG
(Magma) [ n: n in [1..340] | not IsPrime(n) and IsPrime(StringToInteger(IntegerToString(n) cat IntegerToString(NthPrime(n)))) ];
CROSSREFS
KEYWORD
nonn,base,easy,less
AUTHOR
Juri-Stepan Gerasimov, Jan 18 2009
EXTENSIONS
Edited and extended beyond a(4) by Klaus Brockhaus, Jan 20 2009
STATUS
approved