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 A220096 #17 Dec 24 2017 10:36:06
%S A220096 0,1,2,2,4,3,6,4,3,5,10,6,12,7,5,8,16,9,18,10,7,11,22,12,5,13,9,14,28,
%T A220096 15,30,16,11,17,7,18,36,19,13,20,40,21,42,22,15,23,46,24,7,25,17,26,
%U A220096 52,27,11,28,19,29,58,30,60,31,21,32,13,33,66,34,23,35,70
%N A220096 a(1)=0, n-1 if n is prime, else largest proper divisor of n.
%C A220096 On the dual isomorphism [n, n*] this function represents n* - see A091934.
%H A220096 Reinhard Zumkeller, <a href="/A220096/b220096.txt">Table of n, a(n) for n = 1..10000</a>
%F A220096 a(n) = if A220096(n) = 1 then n - 1 else A220096(n). - _Reinhard Zumkeller_, Nov 23 2014
%t A220096 Join[{0}, Table[If[PrimeQ[n], n - 1, Divisors[n][[-2]]], {n, 2, 100}]] (* _T. D. Noe_, Dec 04 2012 *)
%o A220096 (Haskell)
%o A220096 a220096 n = if z == 1 then n - 1 else z where z = a032742 n
%o A220096 -- _Reinhard Zumkeller_, Nov 23 2014
%o A220096 (PARI) a(n) = if (n==1, 0, isprime(n), n-1, my(d=divisors(n)); d[#d-1]); \\ _Michel Marcus_, Dec 24 2017
%Y A220096 Cf. A032742, A091934.
%K A220096 nonn
%O A220096 1,3
%A A220096 _Jon Perry_, Dec 04 2012