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a(n) = prime(prime(prime(n) - 1) - 1) - 1, where prime(n) = n-th prime.
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%I #23 Jan 24 2023 06:58:07

%S 1,2,12,36,106,150,238,280,396,576,612,862,1020,1068,1212,1492,1732,

%T 1810,2088,2346,2410,2712,2902,3220,3582,3906,4020,4210,4336,4512,

%U 5278,5530,5848,6028,6636,6688,7102,7516,7740,8110,8500,8572,9282,9396,9648

%N a(n) = prime(prime(prime(n) - 1) - 1) - 1, where prime(n) = n-th prime.

%p p:=ithprime: seq(p(p(p(n)-1)-1)-1, n=1..53); # _Juri-Stepan Gerasimov_, Oct 25 2009

%t Table[Prime[Prime[Prime[n - 1] - 1] - 1] - 1, {n, 2, 50}] (* _Vincenzo Librandi_, Apr 05 2015 *)

%o (Magma) [NthPrime(NthPrime(NthPrime(n)-1)-1)-1: n in [1..50]]; // _Vincenzo Librandi_, Apr 05 2015

%Y Cf. A141139, A141185. - _Juri-Stepan Gerasimov_, Oct 25 2009

%Y Cf. A140853.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Jul 31 2008

%E a(22) corrected by _D. S. McNeil_, Mar 21 2009