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 A371275 #5 Mar 18 2024 09:51:23
%S A371275 0,1,2,2,1,2,3,3,3,2,3,2,2,1,2,3,3,4,3,4,4,4,3,3,4,4,3,2,3,4,4,3,2,3,
%T A371275 3,3,2,3,2,2,1,2,3,3,4,3,4,4,4,3,4,5,5,4,3,4,5,5,4,4,5,5,5,4,5,4,4,3,
%U A371275 3,4,4,5,4,5,5,5,4,3,4,4,3,2,3,4,4,3,4
%N A371275 a(n) is the number of runs in the balanced ternary expansion of n.
%C A371275 Leading zeros are ignored.
%C A371275 Every positive integers occurs infinitely many times.
%F A371275 a(n) <= A134021(n).
%F A371275 a(A153773(k)) = k for any k > 0.
%e A371275 The first terms, alongside the balanced ternary expansion of n, are:
%e A371275 n a(n) bter(n)
%e A371275 --- ---- -------
%e A371275 0 0 0
%e A371275 1 1 1
%e A371275 2 2 1T
%e A371275 3 2 10
%e A371275 4 1 11
%e A371275 5 2 1TT
%e A371275 6 3 1T0
%e A371275 7 3 1T1
%e A371275 8 3 10T
%e A371275 9 2 100
%e A371275 10 3 101
%e A371275 11 2 11T
%e A371275 12 2 110
%e A371275 13 1 111
%e A371275 14 2 1TTT
%e A371275 15 3 1TT0
%o A371275 (PARI) a(n) = { my (r = 0, d); while (n, r++; d = centerlift(Mod(n, 3)); while (d==centerlift(Mod(n, 3)), n = (n-d)/3;);); return (r); }
%Y A371275 Cf. A005811, A043555, A134021, A153773, A297770.
%K A371275 nonn,base,easy
%O A371275 0,3
%A A371275 _Rémy Sigrist_, Mar 17 2024