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%I #6 Oct 15 2022 16:29:23
%S 4,21,25,205,26707,27679,3066877,3067067,3067097,3067117,3067147,
%T 3067177,3067557,3067567,3067577,3067607,3067717,348933193,348933421,
%U 348933439,44690978633,44690978899,6553736049327,6553736049407,6553736049599,6553736049631,6553736049823,6553736053327,6553736054959
%N Semiprimes k such that k is congruent to 7 modulo k's index in the sequence of semiprimes
%C a(30) > 8040423200947.
%H Lucas A. Brown, <a href="https://github.com/lucasaugustus/oeis/blob/main/semiprimemods.py">semiprimemods.py</a>.
%F a(n) = A001358(A106132(n)).
%e The 1st semiprime is 4, which is congruent to 7 (mod 1), so 4 is in the sequence.
%e The 2nd semiprime is 6, which is not congruent to 7 (mod 2), so 6 is not in the sequence.
%e The 3rd semiprime is 9, which is not congruent to 7 (mod 3), so 9 is not in the sequence.
%e The 7th semiprime is 21, which is congruent to 7 (mod 7), so 21 is in the sequence.
%Y Cf. A001358, A106132.
%K nonn,hard
%O 1,1
%A _Lucas A. Brown_, Oct 15 2022
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