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a(n) = h(n^2) - h(n), where h(n) is the half-totient function (A023022).
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%I #19 Sep 22 2021 12:49:15

%S 2,3,8,5,18,14,24,18,50,22,72,39,56,60,128,51,162,76,120,105,242,92,

%T 240,150,234,162,392,116,450,248,320,264,408,210,648,333,456,312,800,

%U 246,882,430,528,495,1058,376,1008,490,800,612,1352,477,1080,660,1008

%N a(n) = h(n^2) - h(n), where h(n) is the half-totient function (A023022).

%F a(n) = (n-1)*A023022(n), n >= 3.

%o (PARI) h(n) = eulerphi(n)/2;

%o a(n) = h(n^2)-h(n);

%Y Cf. A000010, A023022.

%K nonn

%O 3,1

%A _Jason Earls_, Jul 22 2001