login
A252667
Primes formed by an m-digit prime concatenated with its last (m-1) digits, for m > 1.
1
199, 233, 311, 433, 599, 677, 733, 977, 10303, 10909, 16363, 18181, 22727, 23333, 28181, 30707, 34747, 34949, 35353, 36767, 45757, 48787, 49999, 50909, 52121, 58787, 59393, 59999, 60101, 61717, 63131, 64747, 65353, 66161, 67777, 69191, 72727, 73939, 78787, 80909, 82727, 83939, 94747
OFFSET
1,1
LINKS
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
Cf. A000040.
Sequence in context: A031930 A160342 A225575 * A156840 A227517 A142232
KEYWORD
base,easy,nonn
AUTHOR
Ivan N. Ianakiev, Dec 20 2014
STATUS
approved