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 A358360 #12 Nov 12 2022 11:34:12 %S A358360 0,1,0,2,1,2,0,1,0,3,2,3,1,2,1,3,2,3,0,1,0,2,1,2,0,1,0,4,3,4,2,3,2,4, %T A358360 3,4,1,2,1,3,2,3,1,2,1,4,3,4,2,3,2,4,3,4,0,1,0,2,1,2,0,1,0,3,2,3,1,2, %U A358360 1,3,2,3,0,1,0,2,1,2,0,1,0,5,4,5,3,4,3 %N A358360 The 3-adic valuation of the central Delannoy numbers (sequence A001850). %C A358360 The 3-adic valuation of x is the exponent of the highest power of 3 dividing x. %D A358360 J.-P. Allouche and J. Shallit, Automatic Sequences: Theory, Applications, Generalizations. Cambridge University Press (2003), p. 453. %H A358360 J. Shallit, <a href="https://cs.uwaterloo.ca/~shallit/Talks/kreg7.pdf">k-regular sequences</a>. Talk for the Colloque Michel Mendès France, Bordeaux, France, December 12 2000. %H A358360 Zhao Shen, <a href="https://arxiv.org/abs/2112.11135">On a conjecture of J. Shallit about Apéry-like numbers</a>, arXiv:2112.11135 [math.NT], January 2 2022. %F A358360 b(n) = b(floor(n/3)) + (floor(n/3) mod 2), if n == 0,2 (mod 3); %F A358360 b(n) = b(floor(n/9)) + 1, if n == 1 (mod 3). %F A358360 a(n) = A007949(A001850(n)). %t A358360 Array[IntegerExponent[LegendreP[#, 3], 3] &, 105, 0] (* _Michael De Vlieger_, Nov 12 2022 *) %Y A358360 Cf. A001850, A007949. %K A358360 nonn %O A358360 0,4 %A A358360 _Jeffrey Shallit_, Nov 12 2022