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A092464 Numbers n congruent to 4 or 9 mod 13. 2
4, 9, 17, 22, 30, 35, 43, 48, 56, 61, 69, 74, 82, 87, 95, 100, 108, 113, 121, 126, 134, 139, 147, 152, 160, 165, 173, 178, 186, 191, 199, 204, 212, 217, 225, 230, 238, 243, 251, 256, 264, 269, 277, 282, 290, 295, 303, 308, 316, 321, 329, 334, 342, 347, 355, 360 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers n such that n^2 is congruent to 3 (modulo 13).

LINKS

Table of n, a(n) for n=1..56.

FORMULA

From R. J. Mathar, Apr 20 2009: (Start)

a(n) = a(n-2) + 13 = a(n-1) + a(n-2) - a(n-3) = 13*n/2 - 13/4 - 3*(-1)^n/4.

G.f.: x*(4+5*x+4*x^2)/((1+x)*(x-1)^2).

(End)

a(n) = 13*(n-1) - a(n-1), (with a(1)=4). - Vincenzo Librandi, Nov 17 2010

MATHEMATICA

Select[Range[400], MemberQ[{4, 9}, Mod[#, 13]]&] (* or *) Select[Range[400], PowerMod[#, 2, 13]==3&](* Harvey P. Dale, Mar 05 2012 *)

CROSSREFS

A127547 is a subsequence.

Sequence in context: A313355 A313356 A295494 * A328271 A173562 A161320

Adjacent sequences:  A092461 A092462 A092463 * A092465 A092466 A092467

KEYWORD

nonn

AUTHOR

Jun Mizuki (suzuki32(AT)sanken.osaka-u.ac.jp), Mar 25 2004

EXTENSIONS

More terms from Ray Chandler, Mar 27 2004

Edited by N. J. A. Sloane, May 10 2007

Incorrect formula deleted by N. J. A. Sloane, Jun 16 2010

STATUS

approved

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Last modified September 17 03:42 EDT 2021. Contains 347478 sequences. (Running on oeis4.)