A144589 - OEIS

%I #10 Oct 17 2015 17:20:06

%S 2,7,19,29,53,71,97,103,137,173,193,233,263,271,311,359,409,421,463,

%T 491,503,571,607,647,701,743,757,809,821,839,971,1009,1049,1061,1151,

%U 1181,1231,1283,1303,1367,1429,1451,1543,1553,1579,1601,1699,1831,1873,1879

%N Prime(n-th "prime nonprime").

%F a(n) = prime(A144570(n)).

%p A141468 := proc(n) if n <=2 then n-1; else for a from procname(n-1)+1 do if not isprime(a) then return a; end if; end do: end if; end proc:

%p A144570 := proc(n) A141468(ithprime(n)) ; end proc:

%p A144589 := proc(n) ithprime(A144570(n)) ; end proc:

%p seq(A144589(n),n=1..120) ;  # _R. J. Mathar_, May 01 2010

%o (PARI) c(n) = {for(k=0, primepi(n), isprime(n++)&&k--); n};

%o t(n) = if(n<3,n-1,c(n-2));

%o vector(100, n, prime(t(prime(n)))) \\ _Altug Alkan_, Oct 17 2015

%Y Cf. A000040, A144570.

%K nonn

%O 1,1

%A _Juri-Stepan Gerasimov_, Jan 07 2009, corrected Jan 12 2009

%E Extended by _R. J. Mathar_, May 01 2010