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 A244556 Primes p that do not remain prime if their last digit is replaced by its square. 1

%I

%S 2,3,5,7,43,59,67,79,97,109,113,137,163,167,179,199,227,269,283,293,

%T 313,317,337,349,367,379,397,409,419,439,463,479,487,499,523,557,569,

%U 607,617,619,643,673,677,683,709,719,727,739,743,773,787

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

%H Vincenzo Librandi, <a href="/A244556/b244556.txt">Table of n, a(n) for n = 1..10000</a>

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

%e 727 is in the sequence because 7^2 = 49 and 7249 is not prime.

%t 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 *)

%o (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

%Y Cf. A244555.

%K nonn,base

%O 1,1

%A _Vincenzo Librandi_, Jul 02 2014

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Last modified March 25 04:11 EDT 2023. Contains 361511 sequences. (Running on oeis4.)