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 A221616 Permutation of the minimal 27 balls of a ball clock after a 12-hour period. 1
 3, 26, 13, 2, 21, 16, 8, 14, 6, 18, 5, 12, 10, 11, 9, 20, 4, 23, 19, 25, 1, 27, 22, 17, 7, 15, 24 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The clock has 3 bars with lengths 5, 11, 11. So the minimal number of balls is (5+11+11)+1=27. Use clock(0) PARI script to get the permutation. LINKS dott. Roberto Gobbo, Roll-o-clock Adam Bowman, Ball Clock Gadget PROG (PARI) clock(n) = {vb1 = []; vb2 = []; vb3 = []; nb1 = 5; nb2 = 12; nb3 = 12; nbmin = (nb1-1) + (nb2-1) + (nb3-1)+1; vbn = vector(nbmin+n, x, x); nbt = nb1*nb2*nb3; for (i=1, nbt, ib = vbn[1]; vbn = vector(length(vbn)-1, x, vbn[x+1]); vb1 = concat(vb1, ib); if (length(vb1) == nb1, vb2 = concat(vb2, ib); forstep(j=nb1-1, 1, -1, vbn = concat(vbn, vb1[j]); ); vb1 = []; if (length(vb2) == nb2, vb3 = concat(vb3, ib); forstep(j=nb2-1, 1, -1, vbn = concat(vbn, vb2[j]); ); vb2 = []; if (length(vb3) == nb3, vbn = concat(vbn, ib); forstep(j=nb3-1, 1, -1, vbn = concat(vbn, vb3[j]); ); vb3 = []; ); ); ); /* write("clock.log", "vb1=", vb1); write("clock.log", "vb2=", vb2); write("clock.log", "vb3=", vb3); write("clock.log", "vbN=", vbn); write("clock.log", "-----------"); */ ); return (vbn); } CROSSREFS Cf. A221617. Sequence in context: A307654 A307653 A326610 * A321222 A062181 A058993 Adjacent sequences:  A221613 A221614 A221615 * A221617 A221618 A221619 KEYWORD nonn,fini,full AUTHOR Michel Marcus, Jan 21 2013 STATUS approved

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Last modified April 4 05:13 EDT 2020. Contains 333212 sequences. (Running on oeis4.)