A047210 Largest square modulo n.

0, 1, 1, 1, 4, 4, 4, 4, 7, 9, 9, 9, 12, 11, 10, 9, 16, 16, 17, 16, 18, 20, 18, 16, 24, 25, 25, 25, 28, 25, 28, 25, 31, 33, 30, 28, 36, 36, 36, 36, 40, 39, 41, 37, 40, 41, 42, 36, 46, 49, 49, 49, 52, 52, 49, 49, 55, 57, 57, 49, 60, 59, 58, 57, 64, 64, 65, 64, 64, 65, 64, 64, 72

Offset

1,5

Links

T. D. Noe, Table of n, a(n) for n=1..1000

Eric Weisstein's World of Mathematics, Quadratic Residue

Mathematica

Table[r=Range[n]; Max[Mod[r^2, n]], {n, 100}] (* _T. D. Noe_, Dec 18 2008 *)
Table[r = Range[1 + n/2]; Max[Mod[r^2, n]], {n, 100}] (* _Zak Seidov_, Dec 18 2008 *)

Prog

Contribution from _Michael B. Porter_, May 04 2010: (Start)
(PARI) residue(n, m)={local(r); r=0; for(i=0, floor(m/2), if(i^2%m==n, r=1)); r}
A047210(n)={local(r, m); r=0; m=n; while(r==0, m=m-1; if(residue(m, n), r=1)); m} (End)

Crossrefs

Last elements of rows of A096008.

Sequence in context: A106325 A159835 A240835 * A360915 A120327 A056629

Adjacent sequences: A047207 A047208 A047209 * A047211 A047212 A047213

Keyword

easy,nonn

Author

_Henry Bottomley_, Jun 08 2000

Status

approved