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A226925 Values of n such that L(5) and N(5) 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, 3, -17, 19, -39, 39, -45, -65, 73, -95, -101, 129, -137, -153, 165, 207, -233, 295, -297, -323, 339, -389, 417, 463, 481, -521, -569, -597, -617, -687, 729, 753, -765, 801, -855, -1005, -1025, 1081, 1093, -1115, 1179, -1229, 1231, -1235, -1245, -1275, -1287, 1293, -1319, 1345, -1389, 1417, -1437, 1495, -1521, 1569, 1749, 1755, -1767, -1793, 1807, 1819, -1917 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..295

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 = 5; (* 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 = 2000; 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-Fran├žois 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: A019342 A029473 A103088 * A259772 A082387 A032923

Adjacent sequences:  A226922 A226923 A226924 * A226926 A226927 A226928

KEYWORD

sign

AUTHOR

N. J. A. Sloane, Jul 12 2013

EXTENSIONS

More terms from Vincenzo Librandi, Jul 13 2013

First term added from Bruno Berselli at the suggestion of Vincenzo Librandi, Jul 15 2013

STATUS

approved

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Last modified January 19 09:35 EST 2020. Contains 331048 sequences. (Running on oeis4.)