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A357023
Semiprimes k such that k is congruent to 5 modulo k's index in the sequence of semiprimes.
2
4, 185, 206, 209, 27681, 3066905, 3067135, 3067795, 3067985, 348933197, 348933239, 348933251, 348933257, 348933269, 44690978141, 44690978162, 44690978519, 44690978561, 44690978617, 44690978869, 44690978981, 44690979457, 44690979527, 6553736049293
OFFSET
1,1
COMMENTS
a(32) > 8040423200947.
LINKS
Lucas A. Brown, semiprimemods.py.
FORMULA
a(n) = A001358(A106130(n)).
EXAMPLE
The 1st semiprime is 4, which is congruent to 5 (mod 1), so 4 is in the sequence.
The 2nd semiprime is 6, which is not congruent to 5 (mod 6), so 6 is not in the sequence.
The 60th semiprime is 185, which is congruent to 5 (mod 60), so 185 is in the sequence.
CROSSREFS
Sequence in context: A146549 A156905 A202631 * A102194 A102191 A358809
KEYWORD
nonn,hard
AUTHOR
Lucas A. Brown, Oct 14 2022
STATUS
approved