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 A308094 #15 May 23 2019 01:13:14 %S A308094 1,2,4,8,13,21,10,31,17,34,52,26,45,68,41,66,97,131,57,96,50,139,69, %T A308094 114,165,83,219,107,168,102,158,221,136,198,265,166,3,237,309,386,183, %U A308094 261,140,349,240,319,411,270,363,179,461,322,426,279,381,488,6,364 %N A308094 Arrange distinct numbers in a single square spiral so that the absolute difference between each number and its eight neighbors is unique. %C A308094 Start with 1; always choose smallest number which has not yet appeared. %e A308094 The spiral begins: %e A308094 . %e A308094 673--476--896--714--200--610--848--660--181--831--180 %e A308094 | | %e A308094 877 125--280--513--393----9--336--481--364----6 658 %e A308094 | | | | %e A308094 1085 429 3--166--265--198--136--221--158 488 187 %e A308094 | | | | | | %e A308094 770 554 237 97---66---41---68---45 102 381 647 %e A308094 | | | | | | | | %e A308094 232 7 309 131 13----8----4 26 168 279 18 %e A308094 | | | | | | | | | | %e A308094 743 523 386 57 21 1----2 52 107 426 584 %e A308094 | | | | | | | | | %e A308094 964 14 183 96 10---31---17---34 219 322 12 %e A308094 | | | | | | | %e A308094 1182 405 261 50--139---69--114--165---83 461 842 %e A308094 | | | | | %e A308094 765 539 140--349--240--319--411--270--363--179 680 %e A308094 | | | %e A308094 233 5--685--499---11--572---16--565---19--514---15 %Y A308094 Cf. A175498, A257339. %K A308094 nonn %O A308094 1,2 %A A308094 _Luca Petrone_, May 12 2019