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A156674
Numbers k such that k^2 - 2 == 0 (mod 49).
1
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
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
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Feb 13 2009
EXTENSIONS
Edited by N. J. A. Sloane, Feb 14 2009
STATUS
approved