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 A337063 #18 Sep 18 2020 14:00:40 %S A337063 1,1,4,2,1,3,3,4,4,9,3,3,16,4,4,25,5,1,4,24,6,1,5,10,2,2,9,6,4,14,7,1, %T A337063 6,18,3,5,15,3,6,24,8,2,4,32,8,2,10,10,9,9,16,8,6,15,10,8,16,12,3,7, %U A337063 14,4,18,18,9,15,15,16,16,25,10,10,36,6,6,49,7,3 %N A337063 a(n) = 1 for n < 2; a(n) = freq(a(n-1),n) * freq(a(n-2),n) for n >= 2, where freq(i,j) is the number of times i appears in [a(0),a(1),...,a(j-1)]. %C A337063 Does this sequence contain every number? %C A337063 Does each number appear only a finite number of times? %C A337063 Starting with a(0)=0 and a(1)=1 gives the same sequence offset by one place. %H A337063 Rémy Sigrist, <a href="/A337063/b337063.txt">Table of n, a(n) for n = 0..25000</a> %H A337063 Rémy Sigrist, <a href="/A337063/a337063.gp.txt">PARI program for A337063</a> %e A337063 a(2) = occurrences of a(1)=1 in [a(0), a(1)]=[1, 1] * occurrences of a(0)=1 in [a(0), a(1)]=[1, 1] = 2*2 = 4. %e A337063 a(3) = occurrences of a(2)=4 in [a(0), a(1), a(2)]=[1, 1, 4] * occurrences of a(1)=1 in [a(0), a(1), a(2)]=[1, 1, 4] = 1*2 = 2. %o A337063 (PARI) See Links section. %Y A337063 Cf. A337064 (index of first occurrence of n). %Y A337063 Cf. A316774 (which adds the two previous terms), A316973. %K A337063 nonn %O A337063 0,3 %A A337063 _Alex Lauber_, Aug 13 2020 %E A337063 More terms from _Rémy Sigrist_, Sep 18 2020