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a(n) is the odd part of A318262(n).
1

%I #9 Mar 14 2020 05:21:30

%S 3,3,7,5,3,7,15,5,3,7,15,31,9,5,21,3,7,15,31,63,9,21,3,7,15,31,63,127,

%T 17,9,5,21,85,3,51,7,15,31,63,127,255,17,9,73,5,21,85,3,51,7,15,31,63,

%U 127,255,511,33,17,73,5,21,85,341,11,93,3,51,7,15,31

%N a(n) is the odd part of A318262(n).

%C The odd part of n is the largest odd divisor of n (A000265).

%H Peter Luschny, <a href="/A318261/b318261.txt">Table of n, a(n) for n = 1..1000</a>

%o (Sage)

%o def A318261_list(len):

%o count = 0; n = 0; L = []

%o while count < len:

%o n += 2

%o m = power_mod(2, euler_phi(n), n)

%o if m.is_power_of(2):

%o v = 2^valuation(n, 2)

%o L.append(n // v)

%o count += 1

%o return L

%o print(A318261_list(70))

%Y Cf. A000265, A318262.

%K nonn

%O 1,1

%A _Peter Luschny_, Sep 05 2018