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 A171781 #7 Sep 01 2020 08:42:14 %S A171781 2,3,4,7,8,10,13,15,16,18,20,22,25,27,29,31,32,34,36,38,40,42,44,46, %T A171781 49,51,53,55,57,59,61,63,64,66,68,70,72,74,76,78,80,82,84,86,88,90,92, %U A171781 94,97,99,101,103,105,107,109,111,113,115,117,119,121,123,125 %N A171781 Numbers for which the second bit of the binary expansion is equal to the last bit. %C A171781 Note that A005843 INTERSECT A171781 = A171757. This is an example of two sequences which both have a limiting density, but whose intersection does not. %H A171781 Amiram Eldar, <a href="/A171781/b171781.txt">Table of n, a(n) for n = 1..10000</a> %e A171781 10 is a term since its binary representation is 1010 and both its second and last bits are 0. - _Amiram Eldar_, Sep 01 2020 %t A171781 Select[Range[2, 125], (d = IntegerDigits[#, 2])[[2]] == d[[-1]] &] (* _Amiram Eldar_, Sep 01 2020 *) %Y A171781 Cf. A005843, A171782, A171757, A171763. %K A171781 nonn,base %O A171781 1,1 %A A171781 _N. J. A. Sloane_, Oct 12 2010