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A156674 Numbers n such that n^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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

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

a(n)=a(n-1)+a(n-2)-a(n-3) = 49n/2-49/4+9*(-1)^n/4. G.f.: x(2x+5)(5x+2)/((1+x)(1-x)^2). [From R. J. Mathar, Feb 19 2009]

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 * A022277 A188480 A059722

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

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Last modified July 8 05:33 EDT 2020. Contains 335513 sequences. (Running on oeis4.)