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A162293 Numbers k such that k^2*(k-1)-1 is prime. 6


%S 2,3,4,6,7,9,12,13,18,21,22,30,33,46,48,57,58,61,66,67,75,79,85,87,90,

%T 94,96,99,100,106,111,114,117,118,120,121,127,129,133,138,144,153,160,

%U 162,171,174,175,186,187,195,199,202,204,220,222,223,231,243,246,252

%N Numbers k such that k^2*(k-1)-1 is prime.

%H Ivan Neretin, <a href="/A162293/b162293.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n)^2 * ( a(n)-1 )-1 = A162291(n).

%e a(1)=2 since 2^3-2^2-1=3 is prime.

%e a(2)=3 since 3^3-3^2-1=17 is prime.

%e a(3)=4 since 4^3-4^2-1=47 is prime.

%t lst={};Do[s=n^3-n^2;If[PrimeQ[s-1],AppendTo[lst,n]],{n,6!}];lst

%Y Cf. A087908, A162291 (corresponding k), A111501.

%K nonn

%O 1,1

%A _Vladimir Joseph Stephan Orlovsky_, Jun 30 2009

%E Comments moved to the examples by _R. J. Mathar_, Sep 11 2009

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Last modified July 2 09:21 EDT 2020. Contains 335398 sequences. (Running on oeis4.)