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 A363228 #42 Jun 28 2025 12:26:09
%S A363228 1,2,1,2,1,2,1,3,1,2,1,2,1,2,1,3,1,2,1,2,1,2,1,3,1,2,1,2,1,2,1,4,1,2,
%T A363228 1,2,1,2,1,3,1,2,1,2,1,2,1,3,1,2,1,2,1,2,1,3,1,2,1,2,1,2,1,4,1,2,1,2,
%U A363228 1,2,1,3,1,2,1,2,1,2,1,3,1,2,1,2,1,2,1,3,1,2,1,2,1,2,1,4,1,2,1,2
%N A363228 Exponent of 4 in 9^n - 1.
%C A363228 Not the same as A147648-without-zeros.
%H A363228 Amiram Eldar, <a href="/A363228/b363228.txt">Table of n, a(n) for n = 1..10000</a>
%F A363228 a(n) = floor(A090739(n)/2).
%F A363228 a(n) = A244415(n) + 1.
%F A363228 a(n) = A235127(A024101(n)). - _Michel Marcus_, May 21 2023
%F A363228 Asymptotic mean: Limit_{m->oo} (1/m) * Sum_{k=1..m} a(k) = 5/3. - _Amiram Eldar_, Jul 13 2023
%F A363228 Conjecture: a(n) = A235127(A000045(6*n)), all other 4-adic 6-sections A235127(A000045(.))=0. - _R. J. Mathar_, Jun 28 2025
%t A363228 a[n_] := IntegerExponent[2*n, 4] + 1; Array[a, 100] (* _Amiram Eldar_, May 22 2023 *)
%o A363228 (PARI) a(n) = valuation(2*n, 4) + 1;
%o A363228 (Python)
%o A363228 def A363228(n): return (~n&n-1).bit_length()+3>>1 # _Chai Wah Wu_, Jul 09 2023
%Y A363228 Cf. A007814, A090739, A147648, A244415.
%Y A363228 Cf. A024101, A235127.
%K A363228 nonn,easy
%O A363228 1,2
%A A363228 _Ruud H.G. van Tol_, May 21 2023