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A002504 Numbers x such that 1+3x(x-1) is a ("cuban") prime (cf. A002407).
(Formerly M0522 N0188)

%I M0522 N0188

%S 2,3,4,5,7,10,11,12,14,15,18,24,25,26,28,29,31,33,35,38,39,42,43,46,

%T 49,50,53,56,59,63,64,67,68,75,81,82,87,89,91,92,94,96,106,109,120,

%U 124,126,129,130,137,141,143,148,154,157,158,159,165,166,171,172

%N Numbers x such that 1+3x(x-1) is a ("cuban") prime (cf. A002407).

%D A. J. C. Cunningham, On quasi-Mersennian numbers, Mess. Math., 41 (1912), 119-146.

%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H T. D. Noe, <a href="/A002504/b002504.txt">Table of n, a(n) for n = 1..1000</a>

%e a(1) = 2 since A002407(1)=7=1+3k(k-1) with k=2 is the smallest prime of that form.

%t Select[Range[500], PrimeQ[1 + 3 # (# - 1)] &] (* _T. D. Noe_, Jan 30 2013 *)

%o (PARI) for(k=1,999,isprime(3*k*(k-1)+1)&print1(k",")) \\ - M. F. Hasler, Nov 28 2007

%Y Cf. A002407, A133431.

%K nonn

%O 1,1

%A _N. J. A. Sloane_.

%E Edited, updated (1 is no longer regarded as a prime) and extended by _M. F. Hasler_, Nov 28 2007

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Last modified September 17 03:42 EDT 2021. Contains 347478 sequences. (Running on oeis4.)