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A092021
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Numbers k such that k-th prime + k-th semiprime is semiprime.
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1
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1, 2, 3, 5, 7, 10, 15, 19, 22, 24, 26, 27, 31, 36, 41, 44, 57, 60, 67, 78, 84, 87, 91, 93, 101, 102, 103, 104, 105, 107, 115, 116, 120, 121, 124, 126, 128, 129, 131, 135, 136, 137, 138, 140, 151, 161, 168, 183, 186, 189, 190, 191, 195, 208, 215, 225, 227, 228, 231
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OFFSET
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1,2
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LINKS
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EXAMPLE
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3 is a member because third prime is 5, third semiprime is 9 and 5+9=14 is semiprime.
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MAPLE
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P:= select(isprime, [2, seq(i, i=3..10000, 2)]):
S:= select(t -> numtheory:-bigomega(t)=2, [$4..10000]):
select(t -> numtheory:-bigomega(P[t]+S[t]) = 2, [$1 .. min(nops(P), nops(S))]); # Robert Israel, Nov 15 2023
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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