%I #14 Feb 01 2021 15:43:32
%S 1,2,4,3,6,5,10,7,8,16,12,20,40,24,9,18,36,30,15,45,90,50,14,28,32,64,
%T 48,60,80,120,240,160,72,27,54,108,216,144,150,25,75,180,360,270,100,
%U 42,21,63,126,252,84,96,192,320,480,720,1440,288,576,432,81,162
%N Square spiral of distinct positive integers built by greedy algorithm such that each new value (except the initial one) is a divisor or a multiple of some earlier horizontally or vertically adjacent value.
%C This sequence has similarities with A113552 and A282291, as each term is adjacent to one of its divisors or multiples.
%H Rémy Sigrist, <a href="/A338221/b338221.txt">Table of n, a(n) for n = 0..10200</a>
%H Rémy Sigrist, <a href="/A338221/a338221.png">Colored representation of the spiral for -500 <= x, y <= 500</a> (where the color is function of a(n))
%H Rémy Sigrist, <a href="/A338221/a338221_1.png">Colored representation of the spiral for -500 <= x, y <= 500</a> (where the color is function of A006530(a(n)))
%H Rémy Sigrist, <a href="/A338221/a338221.gp.txt">PARI program for A338221</a>
%e The spiral begins:
%e 216--108---54---27---72--160--240
%e | |
%e 144 36---18----9---24---40 120
%e | | | |
%e 150 30 6----3----4 20 80
%e | | | | | |
%e 25 15 5 1----2 12 60
%e | | | | |
%e 75 45 10----7----8---16 48
%e | | |
%e 180 90---50---14---28---32---64
%e |
%e 360--270--100---42---21---63--126
%o (PARI) See Links section.
%Y Cf. A006530, A113552, A282291.
%K nonn,look
%O 0,2
%A _Rémy Sigrist_, Jan 30 2021