A258332 Numbers n such that 4n + 1, 4n + 2 and 4n + 3 are not squarefree.

211, 420, 722, 906, 2731, 3687, 3962, 4351, 4985, 5505, 5656, 5818, 6162, 6443, 7337, 7562, 7731, 8293, 9175, 9312, 9681, 9861, 10118, 11343, 11918, 11931, 11956, 12093, 12372, 13646, 13756, 13862, 14280, 14618, 14712, 14981, 15306, 15716, 15743, 15961, 16512, 17162, 17237

Offset: 1

Author

Juri-Stepan Gerasimov, May 26 2015

Keywords

• nonn
• easy

Examples

			211 is in this sequence because 4 * 211 + 1 = 845 = 5 * 13^2, 4 * 211 + 2 = 846 = 2 * 3^2 * 47 and 4 * 211 + 3 = 847 = 7 * 11^2.
		

Links

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

Crossrefs

Cf. A188296, A258211.

Programs

Magma

[n: n in [1..20000] | not IsSquarefree(4*n+1) and  not IsSquarefree(4*n+2) and not IsSquarefree(4*n+3)];

Maple

remove(t->ormap(numtheory:-issqrfree,[4*t+1,4*t+2,4*t+3]), [$1..2*10^4]); # Robert Israel, Apr 03 2018

Mathematica

Select[Range[1000], Union[{MoebiusMu[4# + 1], MoebiusMu[4# + 2], MoebiusMu[4# + 3]}] == {0} &] (* Alonso del Arte, May 26 2015 *)

PARI

isok(n) = !issquarefree(4*n+1) && !issquarefree(4*n+2) && !issquarefree(4*n+3); \\ Michel Marcus, Apr 04 2018