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 A056452 a(n) = 6^floor((n+1)/2). 9
 1, 6, 6, 36, 36, 216, 216, 1296, 1296, 7776, 7776, 46656, 46656, 279936, 279936, 1679616, 1679616, 10077696, 10077696, 60466176, 60466176, 362797056, 362797056, 2176782336, 2176782336, 13060694016, 13060694016, 78364164096 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Number of achiral rows of length n using up to six different colors. For a(3) = 36, the rows are AAA, ABA, ACA, ADA, AEA, AFA, BAB, BBB, BCB, BDB, BEB, BFB, CAC, CBC, CCC, CDC, CEC, CFC, DAD, DBD, DCD, DDD, DED, DFD, EAE, EBE, ECE, EDE, EEE, EFE, FAF, FBF, FCF, FDF, FEF, and FFF. - Robert A. Russell, Nov 08 2018 Also: a(n) is the number of palindromes with n digits using a maximum of six different symbols. - David A. Corneth, Nov 09 2018 REFERENCES M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2] LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..2000 Index entries for linear recurrences with constant coefficients, signature (0,6). FORMULA a(n) = 6^floor((n+1)/2). a(n) = 6*a(n-2). - Colin Barker, May 06 2012 G.f.: (1+6*x) / (1-6*x^2). - Colin Barker, May 06 2012 [Adapted to offset 0 by Robert A. Russell, Nov 08 2018] a(n) = C(6,0)*A000007(n) + C(6,1)*A057427(n) + C(6,2)*A056453(n) + C(6,3)*A056454(n) + C(6,4)*A056455(n) + C(6,5)*A056456(n) + C(6,6)*A056457(n). - Robert A. Russell, Nov 08 2018 MAPLE A056452:=n->6^floor((n+1)/2); MATHEMATICA Riffle[6^Range[0, 20], 6^Range[20]] (* Harvey P. Dale, Jun 18 2017 *) Table[6^Ceiling[n/2], {n, 0, 40}] (* or *) LinearRecurrence[{0, 6}, {1, 6}, 40] (* Robert A. Russell, Nov 08 2018 *) PROG (MAGMA) [6^Floor((n+1)/2): n in [0..40]]; // Vincenzo Librandi, Aug 16 2011 CROSSREFS Cf. A016116. Cf. A000400 (oriented), A056308 (unoriented), A350524 (chiral). Sequence in context: A111437 A056464 A056454 * A183622 A176861 A245131 Adjacent sequences:  A056449 A056450 A056451 * A056453 A056454 A056455 KEYWORD nonn,base,easy AUTHOR EXTENSIONS a(0)=1 prepended by Robert A. Russell, Nov 08 2018 Name corrected by David A. Corneth, Nov 08 2018 STATUS approved

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Last modified May 26 13:05 EDT 2019. Contains 323586 sequences. (Running on oeis4.)