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 A155139 Primes p such that both p-+3 are not squarefree. 6

%I #18 Jul 06 2016 02:32:22

%S 47,53,101,239,347,353,487,547,647,653,683,719,853,947,953,1061,1153,

%T 1213,1277,1447,1453,1553,1663,1669,1693,1697,1747,1753,1847,2053,

%U 2153,2251,2347,2447,2647,2659,2741,2753,2887,2953,3041,3253,3347,3359,3433

%N Primes p such that both p-+3 are not squarefree.

%C 47-3=44=2^2*11, 47+3=50=2*5^2, ...

%H John Cerkan, <a href="/A155139/b155139.txt">Table of n, a(n) for n = 1..10000</a>

%t <<NumberTheory`NumberTheoryFunctions` (* needed with older versions *)

%t lst={};Do[p=Prime[n];If[ !SquareFreeQ[p-3]&&!SquareFreeQ[p+3],AppendTo[lst,p]],{n,6!}];lst

%t Select[Prime[Range[500]],!SquareFreeQ[#-3]&&!SquareFreeQ[#+3]&] (* _Harvey P. Dale_, May 01 2012 *)

%o (PARI) lista(nn) = forprime(p=3, nn, if (! issquarefree(p-3) && ! issquarefree(p+3), print1(p, ", "))); \\ _Michel Marcus_, Jul 05 2016

%Y Cf. A153213, A049282.

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Jan 21 2009

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Last modified July 24 22:37 EDT 2024. Contains 374585 sequences. (Running on oeis4.)