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 A086401 #13 Apr 21 2025 02:31:19 %S A086401 0,0,1,1,1,3,1,3,7,8,1,7,1,10,12,11,1,6,1,19,0,3,1,21,1,16,7,5,1,1,1, %T A086401 19,18,20,23,7,1,3,7,17,1,36,1,41,9,26,1,21,1,28,24,45,1,33,18,43,45, %U A086401 32,1,39,1,34,24,51,51,42,1,19,30,7,1,9,1,40,57,57,19,24,1,17,61,44,1,37,51 %N A086401 a(n) = M(n) (mod n) where M(n) = A001006(n) is the n-th Motzkin number. %C A086401 If n is an odd prime a(n) = 1. %H A086401 Amiram Eldar, <a href="/A086401/b086401.txt">Table of n, a(n) for n = 1..10000</a> %F A086401 a(n) = 0 if and only if n is in A266969. - _Amiram Eldar_, Apr 20 2025 %t A086401 motz[0] = motz[1] = 1; motz[n_] := motz[n] = ((2*n + 1)*motz[n-1] + 3*(n-1)*motz[n-2])/(n+2); a[n_] := Mod[motz[n], n]; Array[a, 100] (* _Amiram Eldar_, Apr 20 2025 *) %Y A086401 Cf. A001006, A266969. %K A086401 nonn %O A086401 1,6 %A A086401 _Benoit Cloitre_, Sep 06 2003 %E A086401 Data corrected by _Amiram Eldar_, Apr 20 2025