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 A258332 Numbers n such that 4n + 1, 4n + 2 and 4n + 3 are not squarefree. 2
 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 (list; graph; refs; listen; history; text; internal format)
 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

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Last modified April 23 13:11 EDT 2024. Contains 371913 sequences. (Running on oeis4.)