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 A137235 a(n) = (n+1)/2 if n is odd; a(n) = n/2 + 6 if n is even. 1
 6, 1, 7, 2, 8, 3, 9, 4, 10, 5, 11, 6, 12, 7, 13, 8, 14, 9, 15, 10, 16, 11, 17, 12, 18, 13, 19, 14, 20, 15, 21, 16, 22, 17, 23, 18, 24, 19, 25, 20, 26, 21, 27, 22, 28, 23, 29, 24, 30, 25, 31, 26, 32, 27, 33, 28, 34, 29, 35, 30, 36, 31, 37, 32, 38, 33, 39, 34, 40, 35, 41, 36, 42, 37 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS See the paper by A. Karabegov and J. Holland for details. LINKS A. Karabegov and J. Holland, Finding all solutions to the Magic Hexagram, The College Mathematics Journal, vol. 39 (2008), pp. 102-106. Index entries for linear recurrences with constant coefficients, signature (1,1,-1). FORMULA O.g.f.: -(-6+5*x)/((-1+x)^2 *(1+x)). - R. J. Mathar, Mar 16 2008 a(n) = 1/4*(2*(n + 1) - 11*(-1)^(n + 1) + 11). - Ilya Gutkovskiy, Sep 18 2015 EXAMPLE 0 is even so a(0) = 0/2 + 6 = 6. 1 is odd so a(1) = (1+1)/2 = 1. 2 is even so a(2) = 2/2 + 6 = 7. MAPLE A137235 := proc(n) if n mod 2 = 0 then n/2+6 ; else (n+1)/2 ; fi ; end: seq(A137235(n), n=0..80) ; # R. J. Mathar, Mar 16 2008 MATHEMATICA Table[If[OddQ[n], (n + 1)/2, (n + 12)/2], {n, 0, 60}] (* Erich Friedman, Mar 22 2008 *) a=5; Table[a=n-a, {n, a, 200}] (* Vladimir Joseph Stephan Orlovsky, Nov 22 2009 *) PROG (PARI) a(n)=(2*n+2-11*(-1)^(n+1)+11)/4 \\ Charles R Greathouse IV, Sep 18 2015 CROSSREFS Sequence in context: A113811 A126168 A028323 * A021166 A131231 A200307 Adjacent sequences:  A137232 A137233 A137234 * A137236 A137237 A137238 KEYWORD nonn,easy AUTHOR Parthasarathy Nambi, Mar 08 2008 EXTENSIONS More terms from R. J. Mathar and Erich Friedman, Mar 22 2008, Mar 16 2008 Examples edited by Jon E. Schoenfield, Jan 26 2015 STATUS approved

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Last modified July 22 14:46 EDT 2019. Contains 325224 sequences. (Running on oeis4.)