OFFSET
1,1
LINKS
Ivan N. Ianakiev, Table of n, a(n) for n = 1..1000
EXAMPLE
233 is both prime and concatenation of the 2-digit prime 23 with its last digit 3. Therefore, 233 is in the sequence.
MATHEMATICA
lst1=Prime[Range[5, 1000]]; lst2=Select[ToExpression[StringJoin[Characters[ToString[#]], Drop[Characters[ToString[#]], 1]]&/@lst1], PrimeQ]
Select[Table[FromDigits[Join[IntegerDigits[n], Rest[IntegerDigits[n]]]], {n, Prime[Range[5, 200]]}], PrimeQ] (* Harvey P. Dale, Aug 26 2020 *)
PROG
(PARI) forprime(p=10, 10^3, d=digits(p); if(isprime(10^(#d-1)*p+p%(10^(#d-1))), print1(10^(#d-1)*p+p%(10^(#d-1)), ", "))) \\ Derek Orr, Dec 30 2014
CROSSREFS
KEYWORD
base,easy,nonn
AUTHOR
Ivan N. Ianakiev, Dec 20 2014
STATUS
approved