A068576 Numbers k such that Sum_{j=1..k} mu(j)^2 = floor(6*k/Pi^2).

28, 56, 153, 172, 173, 175, 176, 177, 178, 180, 181, 344, 351, 352, 353, 354, 356, 357, 361, 362, 363, 365, 366, 367, 368, 370, 371, 373, 374, 375, 383, 386, 391, 393, 394, 395, 396, 397, 400, 405, 408, 425, 428, 640, 752, 848, 849, 850, 851, 852, 853, 854

Offset: 1

Author

Benoit Cloitre, Mar 26 2002

Keywords

• easy
• nonn

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A008683, A013928, A059956.

Programs

Mathematica

seq[max_] := Flatten @ Position[Accumulate @ Array[Boole @ SquareFreeQ[#] &, max] - Floor[6*Range[max]/Pi^2], 0]; seq[1000] (* Amiram Eldar, Feb 17 2021 *)

PARI

isok(k) = sum(j=1, k, moebius(j)^2) == 6*k\Pi^2; \\ Michel Marcus, Feb 15 2021