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Lexicographically earliest sequence of numbers in a hexagonal spiral such that their neighbors have no common digit.
2

%I #41 May 31 2024 22:06:46

%S 0,1,2,3,4,5,6,7,8,9,10,44,11,20,13,22,14,23,15,24,16,25,17,26,33,27,

%T 30,28,34,55,29,40,35,60,57,46,37,18,39,47,19,36,45,70,12,48,51,49,31,

%U 50,21,38,41,53,61,42,58,32,80,52,64,59,62,81,56,43,72

%N Lexicographically earliest sequence of numbers in a hexagonal spiral such that their neighbors have no common digit.

%C This sequence ends with 672 terms.

%H Carole Dubois, <a href="/A363765/b363765.txt">Table of n, a(n) for n = 1..672</a>

%H Carole Dubois, <a href="/A363765/a363765_1.jpg">Hexagonal spiral for A363765</a>

%e a(26) = 27 because the neighbors of the 26th hexagon are 10, 30, 33, 44, 48, 51 which have no common digit with 27.

%e a(673) can't be calculated because its neighbors would be 216, 397, and 548, and they use all digits.

%Y Cf. A000384, A003458, A014105, A056105.

%K base,nonn,fini,full

%O 1,3

%A _Carole Dubois_, Jun 20 2023