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