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 A005059 a(n) = (5^n - 3^n)/2. 21
 0, 1, 8, 49, 272, 1441, 7448, 37969, 192032, 966721, 4853288, 24325489, 121804592, 609554401, 3049366328, 15251614609, 76272421952, 381405156481, 1907154922568, 9536162033329, 47681972428112, 238413348924961, 1192077204978008, 5960417405949649 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Number of lines passing through 3 points of an n-dimensional grid of points of side 3. - David W. Wilson, c. 1999 a(n) is also the total number of words of length n, over an alphabet of five letters, one of them appearing an odd number of times. See the Lekraj Beedassy, Jul 22 2003, comment under A006516 (4-letter words), and the Balakrishnan reference there. See A003462 for the analogous 3-letter words problem. - Wolfdieter Lang, Jul 16 2017 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 M. A. Alekseyev and T. Berger, Solving the Tower of Hanoi with Random Moves. In: J. Beineke, J. Rosenhouse (eds.) The Mathematics of Various Entertaining Subjects: Research in Recreational Math, Princeton University Press, 2016, pp. 65-79. ISBN 978-0-691-16403-8 Index entries for linear recurrences with constant coefficients, signature (8,-15). FORMULA a(n) = 8*a(n-1) - 15*a(n-2). - Paul Barry, Mar 03 2003 G.f.: x/((1-3*x)*(1-5*x)). - Paul Barry, Mar 03 2003 a(n) = Sum_{k=1..n} 2^(k-1)*3^(n-k)*binomial(n,k). - Zerinvary Lajos, Sep 24 2006 a(n) = (r^n-s^n)/(r-s) with r=5 and s=3. - Sture Sjöstedt, Oct 17 2012 a(n) = Sum_{k=0..n-1} 3^k*5^(n-k-1) for n>0, a(0)=0. - Bruno Berselli, Aug 07 2013 EXAMPLE For the fifth formula: a(4) = 1*125 + 3*25 + 9*5 + 27*1 = 272. [Bruno Berselli, Aug 07 2013] MAPLE A005059:=n->(5^n-3^n)/2: seq(A005059(n), n=0..30); # Wesley Ivan Hurt, Nov 18 2014 MATHEMATICA Join[{a=0, b=1}, Table[c=8*b-15*a; a=b; b=c, {n, 60}]] (* Vladimir Joseph Stephan Orlovsky, Jan 19 2011 *) LinearRecurrence[{8, -15}, {0, 1}, 50] (* Sture Sjöstedt, Oct 17 2012 *) Table[(5^n - 3^n)/2, {n, 0, 23}] (* Michael De Vlieger, Jul 16 2017 *) PROG (Sage) [lucas_number1(n, 8, 15) for n in range(0, 21)] # Zerinvary Lajos, Apr 23 2009 (Magma) [(5^n - 3^n)/2: n in [0..30] ]; // Vincenzo Librandi, Aug 19 2011 (PARI) a(n)=(5^n-3^n)/2 \\ Charles R Greathouse IV, Jun 11 2013 CROSSREFS Cf. A081199 (binomial transform), A006516 (inverse binomial transform, and special 4-letter words). A003462 (special 3-letter words). Sequence in context: A081901 A283686 A026389 * A026719 A026774 A089383 Adjacent sequences: A005056 A005057 A005058 * A005060 A005061 A005062 KEYWORD nonn,easy AUTHOR N. J. A. Sloane STATUS approved

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Last modified September 23 07:57 EDT 2023. Contains 365544 sequences. (Running on oeis4.)