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If n is prime then a(n) = n, else a(n) = prime(n).
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%I #11 Feb 24 2019 14:44:07

%S 2,2,3,7,5,13,7,19,23,29,11,37,13,43,47,53,17,61,19,71,73,79,23,89,97,

%T 101,103,107,29,113,31,131,137,139,149,151,37,163,167,173,41,181,43,

%U 193,197,199,47,223,227,229,233,239,53,251,257,263,269,271,59,281,61,293

%N If n is prime then a(n) = n, else a(n) = prime(n).

%H Zak Seidov, <a href="/A068519/b068519.txt">Table of n, a(n) for n = 1..1000</a>

%e a(1) = 2 because 1 is not prime, hence a(1) = prime(1) = 2.

%e a(2) = 2 because 2 is prime.

%p seq(`if`(isprime(i), i, ithprime(i)), i=1..100);

%t Table[If[PrimeQ[n],n,Prime[n]],{n,1,200}] (* _Zak Seidov_, Nov 04 2009 *)

%K nonn,easy

%O 1,1

%A Francois Jooste (phukraut(AT)hotmail.com), Mar 18 2002

%E More terms, b-file and Mathematica code from _Zak Seidov_, Nov 04 2009