This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A064921 #11 Jun 21 2018 02:01:38
%S A064921 2,3,3,5,3,7,5,5,3,11,3,13,5,7,5,17,5,19,5,5,3,23,3,5,5,11,3,29,3,31,
%T A064921 17,13,5,11,5,37,5,7,3,41,3,43,5,13,3,47,5,13,5,19,5,53,5,7,5,5,3,59,
%U A064921 5,61,17,7,13,17,5,67,5,5,5,71,5,73,5,19,3,17,5,79,5,29,3,83,5,5,5,31,5
%N A064921 Iterate A064920 until a prime is reached.
%C A064921 Well defined since A064920(n) < n for nonprimes.
%C A064921 a(p) = p for all primes p.
%H A064921 Harry J. Smith, <a href="/A064921/b064921.txt">Table of n, a(n) for n = 2..1000</a>
%e A064921 a(18) = 5 as A064920(18) = 8 and A064920(8) = 5.
%o A064921 (PARI) gpf(n)= { local(f); f=factor(n)~; return(f[1, length(f)]) } { for (n=2, 1000, m=n; while (!isprime(m), g=gpf(m); m=m / g + g - 1); write("b064921.txt", n, " ", m) ) } \\ _Harry J. Smith_, Sep 29 2009
%Y A064921 Cf. A064920, A064922, A064917.
%K A064921 nonn
%O A064921 2,1
%A A064921 _Reinhard Zumkeller_, Oct 14 2001