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 A261366 #11 May 13 2025 02:39:47 %S A261366 0,1,1,2,1,4,3,4,1,8,7,8,5,10,7,8,1,16,15,16,13,18,15,16,9,22,19,20, %T A261366 13,22,15,16,1,32,31,32,29,34,31,32,25,38,35,36,29,38,31,32,17,46,43, %U A261366 44,37,46,39,40,25,50,43,44,29,46,31,32,1,64,63,64,61 %N A261366 a(n) = number of even terms in row n of triangle A261363. %H A261366 Reinhard Zumkeller, <a href="/A261366/b261366.txt">Table of n, a(n) for n = 0..10000</a> %F A261366 For n > 0: a(n) = n + 1 - A001316(n-1). %t A261366 a[n_] := Count[Accumulate[Array[Boole[0 == BitAnd[n - #, #]] &, n + 1, 0]], _?EvenQ]; Array[a, 100, 0] (* _Amiram Eldar_, May 13 2025 *) %o A261366 (Haskell) %o A261366 a261366 = sum . map ((1 -) . flip mod 2) . a261363_row %Y A261366 Cf. A261363, A001316. %K A261366 nonn,easy %O A261366 0,4 %A A261366 _Reinhard Zumkeller_, Aug 16 2015