A395181 - OEIS

%I #20 Apr 23 2026 15:24:10

%S 1,3,8,12,24,48,72,96,120,144,168,192,216,288,360,384,504,528,576,600,

%T 648,768,840,864,960,1080,1152,1344,1368,1440,1536,1584,1680,1728,

%U 1800,1848,1944,2016,2208,2304,2352,2520,2808,2880,3072,3456,3480,3720,4032,4104,4224,4320,4488,4608

%N Values taken by Jordan's totient function J_2, A007434.

%H Miles Englezou, <a href="/A395181/b395181.txt">Table of n, a(n) for n = 1..7248</a>

%e 3 is a term since (2^2-1)*(2^2)^0 = 3.

%e 8 is a term since (3^2-1)*(3^2)^0 = 8.

%e 12 is a term since (2^2-1)*(2^2)^1 = 12.

%e 144 is a term since 3 and 48 are terms, gcd(3, 48) = 1, and 3*48 = 144.

%o (PARI) lst(lim)= my(S = Set()); for(n = 1, lim, my(v = n^2); my(f = factor(n)); for(i = 1, #f~, v *= (1 - 1/f[i,1]^2)); v = numerator(v); if(v <= lim, S = setunion(S, Set([v])))); vecsort(Vec(S))

%Y Cf. A002202, A007434.

%K nonn

%O 1,2

%A _Miles Englezou_, Apr 15 2026