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 A081349 #11 Jan 05 2021 21:31:05 %S A081349 1,2,8,3,7,9,4,6,10,24,15,5,11,23,25,16,14,12,22,26,48,35,17,13,21,27, %T A081349 47,49,36,34,18,20,28,46,50,80,63,37,33,19,29,45,51,79,81,64,62,38,32, %U A081349 30,44,52,78,82,120,99,65,61,39,31,43,53,77,83,119,121,100,98,66,60,40 %N A081349 Square maze arrangement of the natural numbers, read by antidiagonals. %H A081349 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a> %e A081349 Starting with 1,2,3,4, turn (LL) and then repeat (RRR)(LLL) to get: %e A081349 . %e A081349 1 8---9 24 ... %e A081349 | | | | %e A081349 2 7 10 23 ... %e A081349 | | | | %e A081349 3 6 11 22 ... %e A081349 | | | | %e A081349 4---5 12 21 ... %e A081349 | | %e A081349 15--14--13 20 ... %e A081349 | | %e A081349 16--17--18--19 ... %e A081349 ... %Y A081349 Cf. A081344, A093650. %Y A081349 First row is A081351. First column is A081350. %Y A081349 Main diagonal is A081352. Main subdiagonal is 2*A000217(n+1). %K A081349 nonn,tabl %O A081349 0,2 %A A081349 _Paul Barry_, Mar 19 2003