A244555 Primes which remain prime when the last digit is replaced by its square.

11, 13, 17, 19, 23, 29, 31, 37, 41, 47, 53, 61, 71, 73, 83, 89, 101, 103, 107, 127, 131, 139, 149, 151, 157, 173, 181, 191, 193, 197, 211, 223, 229, 233, 239, 241, 251, 257, 263, 271, 277, 281, 307, 311, 331, 347, 353, 359, 373, 383, 389, 401, 421, 431, 433

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..9000

Example

107 is in the sequence because 7^2=49 and 1049 is a prime.
449 is in the sequence because 9^2=81 and 4481 is a prime.

Mathematica

selQ[p_] := (id = IntegerDigits[p]; id1 = Most[id]; id2 = Last[id]^2 // IntegerDigits; p2 = Join[id1, id2] // FromDigits; PrimeQ[p2]); Select[Array[Prime, 100], selQ] (* Jean-François Alcover, Jul 04 2014 *)

Prog

(Magma) r:=func<i | Seqint(Intseq(Intseq(i)[1]^2) cat Intseq(Floor(i/10)))>; [p: p in PrimesUpTo(500) | IsPrime(r(p))]; // Bruno Berselli, Jul 04 2014
(PARI) lista(nn) = {forprime(p=2, nn, d = p % 10; if (isprime(eval(concat(Str(p\10), Str(d^2)))), print1(p, ", ")); ); } \\ Michel Marcus, Jul 04 2014

Crossrefs

Cf. A030430 (subsequence).

Sequence in context: A135779 A135778 A078875 * A052293 A038842 A293660

Adjacent sequences: A244552 A244553 A244554 * A244556 A244557 A244558

Keyword

nonn,base

Author

Vincenzo Librandi, Jul 02 2014

Status

approved