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%I #16 Apr 21 2024 09:59:56
%S 7816642561,49413980161,32713826587115521
%N Carmichael numbers whose index is a power of 2 (see A174590).
%C Carmichael numbers m such that (m-1)/lambda(m) = 2^k for some k, namely for k = 13, 13, 14, ...
%C Composite numbers m for which Od(lambda(m)) = Od(m-1), where Od(m) = A000265(m) is the odd part of m.
%C By Lehmer's totient conjecture, there are no composite numbers m such that Od(phi(m)) = Od(m-1), where phi(m) = A000010(m) and Od(m) as above.
%C a(4) > 10^22, if it exists. - _Amiram Eldar_, Apr 21 2024
%Y Cf. A000010, A000265, A002322, A002997, A174590.
%K nonn,hard,more,bref
%O 1,1
%A _Thomas Ordowski_, Mar 12 2019
%E a(1)-a(3) from _Amiram Eldar_, Mar 12 2019
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