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 A235230 Integer radii of circles tiled by square tiles such that the ratio of uncut tiles to cut tiles is an integer and four square tiles meet at the center of the circle. 1
 1, 6, 15, 364, 585, 5052, 9573, 191714, 13682428 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS It is my conjecture that there are an infinite number of solutions and that they occur by chance, accounting for the widening gaps between valid answers as the number of digits for the sums of tiles increases. The inspiration for this problem came from Enigma #1686 of the New Scientist Magazine. The values involved are the following {a(n), #uncut, cut, ratio} : {1, 0, 4, 0}, {6, 88, 44, 2}, {15, 648, 108, 6}, {364, 414700, 2900, 143}, {585, 1072764, 4644, 231}, {5052, 80161536, 40404, 1984}, {9573, 287864220, 76580, 3759},{191714, 115466138200, 1533700, 75286}, {13682428, 588133849050724, 109459412, 5373077}. No further terms up to 15*10^6. - Giovanni Resta, Jan 06 2014 LINKS New Scientist Magazine, Enigma #1686, 22 February 2012. Giovanni Resta, Illustration for a(2) and a(3) Gregory V. Richardson, QuickBasic 64 program EXAMPLE See picture in Links. PROG See Links. CROSSREFS Sequence in context: A117062 A003155 A199095 * A024081 A145558 A145612 Adjacent sequences:  A235227 A235228 A235229 * A235231 A235232 A235233 KEYWORD nonn,hard,more AUTHOR Gregory V. Richardson, Jan 05 2014 STATUS approved

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Last modified January 22 19:16 EST 2020. Contains 331153 sequences. (Running on oeis4.)