A192450 Numbers k such that -1 is not a square mod k.

3, 4, 6, 7, 8, 9, 11, 12, 14, 15, 16, 18, 19, 20, 21, 22, 23, 24, 27, 28, 30, 31, 32, 33, 35, 36, 38, 39, 40, 42, 43, 44, 45, 46, 47, 48, 49, 51, 52, 54, 55, 56, 57, 59, 60, 62, 63, 64, 66, 67, 68, 69, 70, 71, 72, 75, 76, 77, 78, 79, 80, 81, 83, 84, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 102, 103, 104, 105, 107, 108

Offset: 1

Author

José María Grau Ribas, Jul 01 2011

Keywords

• nonn

Comments

Contains A002145 as a subsequence.

Numbers that are divisible by 4 or by a term of A002145. - Robert Israel, May 14 2020

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A008784, A002145, A334819.

Programs

Maple

filter:= n -> n mod 4 = 0 or member(3, numtheory:-factorset(n) mod 4):
select(filter, [$1..1000]); # Robert Israel, May 14 2020

Mathematica

Table[If[Reduce[x^2==-1,Modulus->n]===False,n],{n,2,200}]//Union

PARI

for(n=1, 1e3, if(!issquare(Mod(-1, n)), print1(n", "))) \\ Charles R Greathouse IV, Jul 04 2011