A252667 Primes formed by an m-digit prime concatenated with its last (m-1) digits, for m > 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

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

Cf. A000040.

Sequence in context: A031930 A160342 A225575 * A156840 A227517 A142232

Adjacent sequences: A252664 A252665 A252666 * A252668 A252669 A252670

Keyword

base,easy,nonn

Author

Ivan N. Ianakiev, Dec 20 2014

Status

approved