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%I #23 Mar 21 2019 07:10:41
%S 9,-15,-95,109,-243,-297,297,457,459,-477,583,723,-761,-771,-983,1045,
%T 1047,1077,1287,1305,-1373,1389,-1481,-2063,-2073,2085,2173,-2223,
%U 2263,-2367,2503,-2591,-2615,-2643,2643,2755,-2955,-2957,2995,3105,-3153,3153,3237,3243,-3267,-3491,3667,3699,3847,3919,-4023,-4217,4255,-4275,4377,4483,4549,4743,4827,4855,-4973
%N Values of n such that L(7) and N(7) are both prime, where L(k) = (n^2+n+1)*2^(2*k) + (2*n+1)*2^k + 1, N(k) = (n^2+n+1)*2^k + n.
%C Computed with PARI using commands similar to those used to compute A226921.
%H Vincenzo Librandi and Joerg Arndt, <a href="/A226927/b226927.txt">Table of n, a(n) for n = 1..1000</a>
%H Eric L. F. Roettger, <a href="http://people.ucalgary.ca/~hwilliam/files/A_Cubic_Extention_of_the_Lucas_Functions.pdf">A cubic extension of the Lucas functions</a>, Thesis, Dept. of Mathematics and Statistics, Univ. of Calgary, 2009. See page 195.
%t k = 7; (* adjust for related sequences *) fL[n_] := (n^2 + n + 1)*2^(2*k) + (2*n + 1)*2^k + 1; fN[n_] := (n^2 + n + 1)*2^k + n; nn = 5000; A = {}; For[n = -nn, n <= nn, n++, If[PrimeQ[fL[n]] && PrimeQ[fN[n]], AppendTo[A, n]]]; cmpfunc[x_, y_] := If[x == y, Return[True], ax = Abs[x]; ay = Abs[y]; If[ax == ay, Return[x < y], Return[ ax < ay]]]; Sort[A, cmpfunc] (* _Jean-François Alcover_, Jul 17 2013, translated and adapted from Joerg Arndt's Pari program in A226921 *)
%Y Cf. A226921-A226929, A227448, A227449, A227515-A227523.
%K sign
%O 1,1
%A _N. J. A. Sloane_, Jul 12 2013
%E More terms from _Vincenzo Librandi_, Jul 13 2013
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