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 A090964 #4 Mar 31 2012 13:20:56 %S A090964 1,4,2,5,3,8,6,9,7,12,10,13,11,16,14,17,15,20,18,21,19,24,22,25,23,28, %T A090964 26,29,27,32,30,33,31,36,34,37,35,40,38,41,39,44,42,45,43,48,46,49,47, %U A090964 52,50,53,51,56,54,57,55,60,58,61,59,64,62,65,63,68,66,69,67,72,70,73 %N A090964 Permutation of natural numbers generated by 2-rowed array shown below. %C A090964 1 4 5 8 9 12 13 16 17 20...(A042948) %C A090964 2 3 6 7 10 11 14 15 18 19...(A042964) %F A090964 For n > 1, a(n+8) = a(n)+8. - _David Wasserman_, Feb 23 2006 %K A090964 nonn %O A090964 0,2 %A A090964 _Giovanni Teofilatto_, Feb 29 2004 %E A090964 More terms from _David Wasserman_, Feb 23 2006