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A357781
Semiprimes k such that k is congruent to 1 modulo k's index in the sequence of semiprimes.
2
4, 82, 85, 106, 121, 133, 142, 166, 169, 217, 3067001, 3067006, 3067286, 3067411, 3067651, 3067691, 3067721, 3067751, 3067771, 3067781, 3067801, 3068071, 348933121, 348933127, 348933199, 348933223, 348933241, 348933259, 348933271, 348933427, 44690978221, 44690978543, 44690978669
OFFSET
1,1
COMMENTS
a(45) > 8040423200947.
LINKS
Lucas A. Brown, semiprimemods.py
FORMULA
a(n) = A001358(A106126(n)).
EXAMPLE
The 1st semiprime is 4, which is congruent to 1 (mod 1), so 4 is in the sequence.
The 4th semiprime is 10, which is congruent to 2 (mod 4), so 10 is not in the sequence.
The 27th semiprime is 82, which is congruent to 1 (mod 27), so 82 is in the sequence.
CROSSREFS
Sequence in context: A090599 A133396 A233001 * A318868 A289224 A158981
KEYWORD
nonn,hard
AUTHOR
Lucas A. Brown, Oct 13 2022
STATUS
approved