A156674 Numbers k such that k^2 - 2 == 0 (mod 49).

10, 39, 59, 88, 108, 137, 157, 186, 206, 235, 255, 284, 304, 333, 353, 382, 402, 431, 451, 480, 500, 529, 549, 578, 598, 627, 647, 676, 696, 725, 745, 774, 794, 823, 843, 872, 892, 921, 941, 970, 990, 1019, 1039, 1068, 1088, 1117, 1137, 1166, 1186, 1215

Offset

1,1

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (1, 1, -1).

Formula

G.f.: (10*x^2 + 29*x + 10)/(x^3 - x^2 - x + 1). - Alexander R. Povolotsky, Feb 15 2009

From R. J. Mathar, Feb 19 2009: (Start)

a(n) = a(n-1) + a(n-2) - a(n-3) = 49*n/2 - 49/4 + 9*(-1)^n/4.

G.f.: x*(2x+5)*(5x+2)/((1+x)*(1-x)^2). (End)

Example

10^2 - 2 == 0 (mod 49);
39^2 - 2 == 0 (mod 49);
59^2 - 2 == 0 (mod 49);
88^2 - 2 == 0 (mod 49).

Mathematica

With[{c = 7^2}, Select[Range[1500], Divisible[#^2 - 2, c]&]] (* Vincenzo Librandi, Apr 06 2013 *)

Prog

(Magma) [Floor(n/2)*49-10*(-1)^n: n in [1..50]]; // Vincenzo Librandi, Apr 06 2013

Crossrefs

Sequence in context: A216591 A249707 A228140 * A360669 A022277 A348617

Adjacent sequences: A156671 A156672 A156673 * A156675 A156676 A156677

Keyword

nonn,easy

Author

Vincenzo Librandi, Feb 13 2009

Extensions

Edited by N. J. A. Sloane, Feb 14 2009

Status

approved