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 A307834 Counterclockwise square spiral constructed by greedy algorithm such that the sum of the values of any two vertically or horizontally adjacent cells is unique. 4
 0, 0, 1, 2, 2, 5, 1, 8, 10, 1, 12, 13, 2, 15, 17, 18, 3, 20, 19, 25, 2, 27, 22, 21, 32, 2, 35, 26, 28, 38, 4, 43, 31, 31, 32, 48, 4, 52, 37, 39, 34, 58, 6, 63, 40, 46, 49, 39, 70, 5, 76, 42, 56, 51, 45, 80, 5, 86, 44, 62, 66, 67, 46, 96, 5, 100, 50, 71, 72, 76 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 COMMENTS Visually, we have a superposition of two images that we can separate by considering the parity of the sum of the x and y coordinates (see illustrations in Links section). LINKS Rémy Sigrist, Table of n, a(n) for n = 0..10200 (-50 <= x <= 50 and -50 <= y <= 50) Peter Kagey and Rémy Sigrist, Colored representation of z(2*k)/abs(z(2*k))*a(2*k) for k = 1..501000 (where z(n) = A174344(n) + i*A274923(n) and the hue is function of k) Peter Kagey and Rémy Sigrist, Colored representation of z(2*k-1)/abs(z(2*k-1))*a(2*k-1) for k = 1..501000 (where z(n) = A174344(n) + i*A274923(n) and the hue is function of k) Rémy Sigrist, PARI program for A307834 EXAMPLE The spiral begins:     8--158---69--111---91---95---93--110---61--147----6     |                                                 |   164    5---96---46---67---66---62---44---86----5  140     |    |                                       |    |    67  100    4---48---32---31---31---43----4   80   64     |    |    |                             |    |    |   123   50   52    3---18---17---15----2   38   45   96     |    |    |    |                   |    |    |    |    97   71   37   20    2----2----1   13   28   51   88     |    |    |    |    |         |    |    |    |    |   102   72   39   19    5    0----0   12   26   56   82     |    |    |    |    |              |    |    |    |    99   76   34   25    1----8---10----1   35   42   94     |    |    |    |                        |    |    |   123   56   58    2---27---22---21---32----2   76   55     |    |    |                                  |    |    71  106    6---63---40---46---49---39---70----5  130     |    |                                            |   172    9--110---54---80---76---75---84---56--122----7     |    10--182---73--133--109--117--120--112--141---76--193 PROG (PARI) See Links section. CROSSREFS See A307838 for the multiplicative variant. Cf A174344, A274923. Sequence in context: A274847 A165922 A337293 * A326616 A249033 A068762 Adjacent sequences:  A307831 A307832 A307833 * A307835 A307836 A307837 KEYWORD nonn,look AUTHOR Rémy Sigrist, May 01 2019 STATUS approved

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Last modified January 16 15:53 EST 2021. Contains 340206 sequences. (Running on oeis4.)