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

1,1

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

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

Prog

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

Crossrefs

Cf. A008784, A002145, A334819.

Sequence in context: A188435 A047517 A206587 * A039064 A187953 A188024

Adjacent sequences: A192447 A192448 A192449 * A192451 A192452 A192453

Keyword

nonn

Author

José María Grau Ribas, Jul 01 2011

Status

approved