A244556 - OEIS

A244556

Primes p that do not remain prime if their last digit is replaced by its square.

2, 3, 5, 7, 43, 59, 67, 79, 97, 109, 113, 137, 163, 167, 179, 199, 227, 269, 283, 293, 313, 317, 337, 349, 367, 379, 397, 409, 419, 439, 463, 479, 487, 499, 523, 557, 569, 607, 617, 619, 643, 673, 677, 683, 709, 719, 727, 739, 743, 773, 787

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..10000

EXAMPLE

59 is in the sequence because 9^2 = 81 and 581 is not prime.

727 is in the sequence because 7^2 = 49 and 7249 is not 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] (* see Jean-François Alcover in A244555 *)

PROG

(Magma) r:=func<i | Seqint(Intseq(Intseq(i)[1]^2) cat Intseq(Floor(i/10)))>; [p: p in PrimesUpTo(800) | not IsPrime(r(p))]; // Bruno Berselli, Jul 04 2014

CROSSREFS

Cf. A244555.

Sequence in context: A286319 A090716 A083820 * A279954 A120804 A092066

Adjacent sequences: A244553 A244554 A244555 * A244557 A244558 A244559

KEYWORD

nonn,base

AUTHOR

Vincenzo Librandi, Jul 02 2014

STATUS

approved