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A356755
Semiprimes k such that k is congruent to 2 modulo k's index in the sequence of semiprimes.
1
4, 6, 10, 119, 155, 158, 215, 27682, 3066887, 3066907, 3067027, 3067167, 3067187, 3067247, 3067277, 3067682, 3067687, 3067742, 3067787, 3067847, 3067907, 3067917, 3067937, 3067942, 3068042, 3068067, 348933302, 348933422, 44690978131, 44690978257, 44690978537, 44690978719, 44690978971
OFFSET
1,1
COMMENTS
a(34) > 8040423200947.
FORMULA
a(n) = A001358(A106127(n)).
EXAMPLE
The 1st semiprime is 4, which is congruent to 2 (mod 1), so 4 is in the sequence.
The 2nd semiprime is 6, which is congruent to 2 (mod 2), so 6 is in the sequence.
The 3rd semiprime is 9, which is congruent to 0 (mod 3), so 9 is not in the sequence.
The 4th semiprime is 10, which is congruent to 2 (mod 4), so 10 is in the sequence.
CROSSREFS
Sequence in context: A136838 A234276 A274991 * A109378 A132149 A129235
KEYWORD
nonn,hard
AUTHOR
Lucas A. Brown, Oct 13 2022
STATUS
approved