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A192450
Numbers k such that -1 is not a square mod k.
4
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
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
KEYWORD
nonn
AUTHOR
STATUS
approved