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 A181281 A version of Josephus problem: a(n) is the surviving integer under the following elimination process. Arrange 1,2,3,...,n in a circle, increasing clockwise. Starting with i=1, delete the integer 4 places clockwise from i. Repeat, counting 4 places from the next undeleted integer, until only one integer remains. 5
 1, 2, 1, 2, 2, 1, 6, 3, 8, 3, 8, 1, 6, 11, 1, 6, 11, 16, 2, 7, 12, 17, 22, 3, 8, 13, 18, 23, 28, 3, 8, 13, 18, 23, 28, 33, 1, 6, 11, 16, 21, 26, 31, 36, 41, 46, 4, 9, 14, 19, 24, 29, 34, 39, 44, 49, 54, 1, 6, 11, 16, 21, 26, 31, 36, 41, 46, 51, 56, 61, 66, 71, 3, 8, 13, 18, 23, 28, 33, 38 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES Paul Weisenhorn, Josephus und seine Folgen, MNU Journal (Der mathematische und naturwissenschaftliche Unterricht), 59 (2006), 18-19. LINKS FORMULA a(n) = (a(n-1) + 4) mod n + 1 if n>1, a(1) = 1. EXAMPLE a(7) = 6: (^1,2,3,4,5,6,7) -> (1,2,3,4,^6,7) -> (1,2,^4,6,7) -> (1,^4,6,7) -> (1,^6,7) -> (^1,6) -> (^6). a(14) = 11 => a(15) = (a(14)+4) mod 15 + 1 = 1. MAPLE a:= proc(n) option remember;       `if` (n=1, 1, (a(n-1)+4) mod n +1)     end: seq (a(n), n=1..100); MATHEMATICA a[1] = 1; a[n_] := a[n] = Mod[a[n-1]+4, n]+1; Table[a[n], {n, 1, 80}] (* Jean-François Alcover, Oct 18 2013 *) CROSSREFS Cf. A006257, A054995, A088333. Sequence in context: A173410 A166548 A273138 * A171683 A249130 A134997 Adjacent sequences:  A181278 A181279 A181280 * A181282 A181283 A181284 KEYWORD nonn AUTHOR Paul Weisenhorn, Oct 10 2010 EXTENSIONS Edited by Alois P. Heinz, Sep 06 2011 STATUS approved

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Last modified October 27 15:27 EDT 2020. Contains 338035 sequences. (Running on oeis4.)