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a(n) is the least prime greater than 3*prime(n).
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%I #14 Feb 16 2024 15:08:04

%S 7,11,17,23,37,41,53,59,71,89,97,113,127,131,149,163,179,191,211,223,

%T 223,239,251,269,293,307,311,331,331,347,383,397,419,419,449,457,479,

%U 491,503,521,541,547,577,587,593,599,641,673,683,691,701,719,727,757

%N a(n) is the least prime greater than 3*prime(n).

%F a(n) = A151800(A001748(n)).

%e 5 < 3*2 < 7 < 3*3 < 11 < 13 < 3*5 < 17, so (a(1), a(2), a(3)) = (7,11,17).

%t Table[NextPrime[Prime[PrimePi[3*Prime[n]]]], {n,1,200}]

%o (PARI) a(n) = nextprime(3*prime(n)); \\ _Michel Marcus_, Feb 10 2024

%Y Cf. A000040, A001748, A059786, A059788, A151800, A370008.

%K nonn

%O 1,1

%A _Clark Kimberling_, Feb 09 2024