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Numbers k such that A296992(k) = 2.
3

%I #22 Feb 16 2025 08:33:52

%S 3,9,12,18,21,27,36,40,42,48,54,72,81,84,108,120,135,144,162,168,189,

%T 192,216,243,270,280,324,336,360,378,432,448,486,540,576,640,648,672,

%U 729,756,768,828,840,864,945,972,1080,1152,1296,1344,1458,1512,1701,1728,1890

%N Numbers k such that A296992(k) = 2.

%H Amiram Eldar, <a href="/A297001/b297001.txt">Table of n, a(n) for n = 1..250</a>

%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TauFunction.html">Tau Function</a>.

%t 1 + Position[Table[-1 + SelectFirst[Range[0, 5], !Divisible[RamanujanTau@ n, n^#] &], {n, 2, 2000}], 2][[All, 1]] (* _Michael De Vlieger_, Dec 23 2017 *)

%o (PARI) isok(k) = if(k == 1, 0, valuation(ramanujantau(k), k) == 2); \\ _Amiram Eldar_, Jan 09 2025

%Y Cf. A000594, A296991, A296992, A297000.

%K nonn,changed

%O 1,1

%A _Seiichi Manyama_ and _Robert G. Wilson v_, Dec 23 2017