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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.
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%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