A308776 Counterclockwise square spiral of distinct positive integers constructed by greedy algorithm, such that for k = 1..5, every term equal to k mod 5 (except k itself) is vertically or horizontally adjacent to a cell already holding a value equal to k mod 5.
1, 2, 3, 4, 5, 6, 11, 16, 7, 12, 17, 8, 13, 18, 9, 10, 15, 20, 21, 26, 31, 36, 41, 22, 27, 32, 37, 42, 23, 28, 33, 38, 43, 14, 19, 24, 29, 25, 30, 35, 40, 45, 50, 46, 51, 56, 47, 52, 57, 62, 67, 72, 77, 48, 53, 58, 63, 68, 73, 78, 34, 39, 44, 49, 54, 59, 55
Offset: 1
Keywords
Examples
The spiral begins:
89---84---79---74---69---64--123--118--113--108--103
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94 54---49---44---39---34---78---73---68---63 98
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99 59 29---24---19---14---43---38---33 58 93
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95 55 25 15---10----9---18---13 28 53 88
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100 60 30 20 5----4----3 8 23 48 83
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105 65 35 21 6 1----2 17 42 77 112
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110 70 40 26 11---16----7---12 37 72 107
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115 75 45 31---36---41---22---27---32 67 102
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120 80 50---46---51---56---47---52---57---62 97
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125 85---90---61---66---71---76---81---82---87---92
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130--135--140---86---91---96--101--106--111--116--117
Links
- Rémy Sigrist, Table of n, a(n) for n = 1..10201
- Rémy Sigrist, Colored representation of the spiral for -500 <= x <= 500 and -500 <= y <= 500 (where the color is function of a(n) mod 5)
- Rémy Sigrist, Colored scatterplot of (n, a(n)-n) for n = 1..40401 (where the color is function of a(n) mod 5)
- Rémy Sigrist, PARI program for A308776
Programs
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PARI
See Links section.
Comments