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

1,1

Links

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

Example

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.

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 *)

Prog

(Magma) [n: n in [1..20000] | not IsSquarefree(4*n+1) and  not IsSquarefree(4*n+2) and not IsSquarefree(4*n+3)];
(PARI) isok(n) = !issquarefree(4*n+1) && !issquarefree(4*n+2) && !issquarefree(4*n+3); \\ Michel Marcus, Apr 04 2018

Crossrefs

Cf. A188296, A258211.

Sequence in context: A142288 A147156 A140535 * A073102 A076167 A217620

Adjacent sequences: A258329 A258330 A258331 * A258333 A258334 A258335

Keyword

nonn,easy

Author

Juri-Stepan Gerasimov, May 26 2015

Status

approved