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%I #28 Apr 21 2024 09:59:48
%S 2320690177,17069520863233,42182344790209,65465530560001,
%T 3432376805760001,13322002122777601,20388795375960001,
%U 129009714848870401,580007888606160001,1096591987029196801,3029756968906340401,5806765663003468801,6213994663149504001,6367205158826803201,7802569551798000001,10319507991273499201
%N Numbers k > 2 such that lambda(k)^2 divides k-1, where lambda(k) = A002322(k).
%C Squarefree numbers k > 2 such that (p-1)^2 | k-1 for every prime p|k.
%C For the first five terms, lambda(k)^2 | phi(k). - _Thomas Ordowski_, Apr 11 2017
%H Amiram Eldar, <a href="/A277720/b277720.txt">Table of n, a(n) for n = 1..47</a> (terms below 10^22, calculated using data from Claude Goutier)
%H Claude Goutier, <a href="http://www-labs.iro.umontreal.ca/~goutier/OEIS/A055553/">Compressed text file carm10e22.gz containing all the Carmichael numbers up to 10^22</a>.
%o (PARI) isok(n) = (n % lcm(znstar(n)[2])^2) == 1; \\ _Michel Marcus_, Apr 22 2017
%Y Subsequence of A002997 and of A277389.
%Y Cf. A002322.
%K nonn
%O 1,1
%A _Thomas Ordowski_ and _Charles R Greathouse IV_, Oct 28 2016
%E a(7)-a(16) from _Max Alekseyev_, Apr 23 2017