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Semiprimes whose both factors are Fermat primes.
6

%I #11 Apr 15 2020 21:08:25

%S 9,15,25,51,85,289,771,1285,4369,66049,196611,327685,1114129,16843009,

%T 4295098369

%N Semiprimes whose both factors are Fermat primes.

%C Product of two, not necessarily distinct Fermat primes.

%C For the finiteness or non-finiteness of this sequence, see A019434.

%C Most terms are binary palindromes (in A006995), except among the fifteen known terms, these squares > 9 are not: 25, 289, 66049, 4295098369.

%Y Cf. A006995, A019434.

%Y Subsequence of A334102.

%K nonn

%O 1,1

%A _Antti Karttunen_, Apr 15 2020