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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
Sequence in context: A057630 A057628 A144364 * A031372 A028877 A087394
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.)