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%I
%S 443372888629441,39671149333495681,842526563598720001,
%T 2380296518909971201,3188618003602886401
%N Carmichael numbers of order 2.
%C Odd composite integer n is in this sequence if n == 1 or p (mod p^2 - 1) for every prime p|n.
%C No other terms below 10^21.
%H Everett W. Howe, <a href="https://doi.org/10.1090/S0025-5718-00-01225-4">Higher-order Carmichael numbers</a>, Math. Comp. 69 (2000), 1711-1719. doi:10.1090/S0025-5718-00-01225-4
%Y Subsequence of A002997, A175530, and A299799.
%K nonn,hard,more
%O 1,1
%A _Max Alekseyev_, Jun 08 2010
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