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A333788 Semiprimes whose both factors are Fermat primes. 5
9, 15, 25, 51, 85, 289, 771, 1285, 4369, 66049, 196611, 327685, 1114129, 16843009, 4295098369 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Product of two, not necessarily distinct Fermat primes.

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

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

LINKS

Table of n, a(n) for n=1..15.

CROSSREFS

Cf. A006995, A019434.

Subsequence of A334102.

Sequence in context: A109888 A193227 A014003 * A082549 A013569 A129401

Adjacent sequences:  A333785 A333786 A333787 * A333789 A333790 A333791

KEYWORD

nonn

AUTHOR

Antti Karttunen, Apr 15 2020

STATUS

approved

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Last modified April 16 04:49 EDT 2021. Contains 343030 sequences. (Running on oeis4.)