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 A226922 Values of n such that L(2) and N(2) 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. 1
 -1, 1, -11, 31, 55, 115, -191, -221, 271, 361, -515, 601, -641, -695, 745, -1061, 1075, 1201, -1259, 1399, 1495, 1651, 1669, 1915, -2381, 2449, -2921, 2959, -2969, 2971, -3035, 3049, -3215, 3265, -3419, -3611, 3709, 3889, 4045, -4229, -4241, -4301, 4561, -4565, -4589, -4721, 4849, -4931, -5039, -5081, -5555, -5795, 5821, -5879, -5921 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Computed with PARI using commands similar to those used to compute A226921. LINKS Vincenzo Librandi and Joerg Arndt, Table of n, a(n) for n = 1..1000 Eric L. F. Roettger, A cubic extension of the Lucas functions, Thesis, Dept. of Mathematics and Statistics, Univ. of Calgary, 2009. See page 195. MATHEMATICA k = 2; (* 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 = 6000; 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 *) CROSSREFS Cf. A226921-A226929, A227448, A227449, A227515-A227523. Sequence in context: A057630 A057628 A144364 * A031372 A028877 A087394 Adjacent sequences: A226919 A226920 A226921 * A226923 A226924 A226925 KEYWORD sign AUTHOR N. J. A. Sloane, Jul 12 2013 EXTENSIONS More terms from Vincenzo Librandi, Jul 13 2013 First two terms added from Bruno Berselli, at the suggestion of Vincenzo Librandi, Jul 15 2013 STATUS approved

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Last modified May 23 05:11 EDT 2024. Contains 372758 sequences. (Running on oeis4.)