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 A054084 #14 Aug 25 2022 16:54:57 %S A054084 2,1,5,3,7,4,10,6,13,8,15,9,18,11,20,12,23,14,26,16,28,17,31,19,34,21, %T A054084 36,22,39,24,41,25,44,27,47,29,49,30,52,32,54,33,57,35,60,37,62,38,65, %U A054084 40,68,42,70,43,73,45,75,46,78,48,81,50,83 %N A054084 Permutation of N: for each k >= 1, let p(k)=least natural number not already an a(i), q(k)=p(k)+k, a(2k-1)=q(k), a(2k)=p(k). %H A054084 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %o A054084 (Python) %o A054084 from math import isqrt %o A054084 def A054084(n): return ((m:=n+1>>1)+isqrt(5*m**2)>>1)+m*(n&1) # _Chai Wah Wu_, Aug 25 2022 %Y A054084 Cf. A054082, A054085. %Y A054084 Odd-indexed terms: A001950 (Upper Wythoff sequence). Even-indexed terms: A000201 (Lower Wythoff sequence). Inverse permutation: A064786. %K A054084 nonn,eigen %O A054084 1,1 %A A054084 _Clark Kimberling_