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A070441 n^2 mod 19. 4
0, 1, 4, 9, 16, 6, 17, 11, 7, 5, 5, 7, 11, 17, 6, 16, 9, 4, 1, 0, 1, 4, 9, 16, 6, 17, 11, 7, 5, 5, 7, 11, 17, 6, 16, 9, 4, 1, 0, 1, 4, 9, 16, 6, 17, 11, 7, 5, 5, 7, 11, 17, 6, 16, 9, 4, 1, 0, 1, 4, 9, 16, 6, 17, 11, 7, 5, 5, 7, 11, 17, 6, 16, 9, 4, 1, 0, 1, 4, 9, 16, 6, 17, 11, 7, 5, 5, 7, 11 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

x^2 - k = 19*y, where x, y and k are integers, has solutions if and only if k mod 19 is an element of {0,1,4,5,6,7,9,11,16,17}. - Vincenzo Librandi, Aug 12 2014

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 0..200

FORMULA

a(n+19) = a(n).

a(19*k - n) = a(n). - Robert Israel, Aug 12 2014

MAPLE

A070441:=n->n^2 mod 19: seq(A070441(n), n=0..100); # Wesley Ivan Hurt, Aug 12 2014

MATHEMATICA

Table[Mod[n^2, 19], {n, 0, 200}] (* Vladimir Joseph Stephan Orlovsky, Apr 23 2011 *)

PowerMod[Range[0, 90], 2, 19] (* Harvey P. Dale, Mar 23 2012 *)

PROG

(MAGMA) [n^2 mod(19): n in [0..100]]; // Vincenzo Librandi, Aug 12 2014

(PARI) a(n)=n^2%19 \\ Charles R Greathouse IV, Apr 06 2016

CROSSREFS

Cf. A070442, A070443, A070444.

Sequence in context: A070442 A086957 A096879 * A070440 A054580 A165488

Adjacent sequences:  A070438 A070439 A070440 * A070442 A070443 A070444

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane, May 12 2002

STATUS

approved

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Last modified October 19 03:10 EDT 2021. Contains 348073 sequences. (Running on oeis4.)