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 A052918 a(0) = 1, a(1) = 5, a(n+1) = 5*a(n) + a(n-1). 42
 1, 5, 26, 135, 701, 3640, 18901, 98145, 509626, 2646275, 13741001, 71351280, 370497401, 1923838285, 9989688826, 51872282415, 269351100901, 1398627786920, 7262490035501, 37711077964425, 195817879857626 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A087130(n)^2 - 29*a(n-1)^2 = 4*(-1)^n, n >= 1. - Gary W. Adamson, Jul 01 2003, corrected Oct 07 2008, corrected by Jianing Song, Feb 01 2019 a(p) == 29^((p-1)/2)) (mod p), for odd primes p. - Gary W. Adamson, Feb 22 2009 For more information about this type of recurrence, follow the Khovanova link and see A054413, A086902 and A178765. - Johannes W. Meijer, Jun 12 2010 Binomial transform of A015523. - Johannes W. Meijer, Aug 01 2010 For positive n, a(n) equals the permanent of the n X n tridiagonal matrix with 5's along the main diagonal and 1's along the superdiagonal and the subdiagonal. - John M. Campbell, Jul 08 2011 a(n) equals the number of words of length n on alphabet {0,1,...,5} avoiding runs of zeros of odd lengths. - Milan Janjic, Jan 28 2015 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 D. Birmajer, J. B. Gil, M. D. Weiner, n the Enumeration of Restricted Words over a Finite Alphabet , J. Int. Seq. 19 (2016) # 16.1.3, Example 8. INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 901 M. Janjic, Hessenberg Matrices and Integer Sequences , J. Int. Seq. 13 (2010) # 10.7.8, section 3. M. Janjic, On Linear Recurrence Equations Arising from Compositions of Positive Integers, Journal of Integer Sequences, Vol. 18 (2015), Article 15.4.7. Tanya Khovanova, Recursive Sequences Index entries for linear recurrences with constant coefficients, signature (5,1). FORMULA G.f.: 1/(1 - 5*x - x^2). a(3n) = A041047(5n), a(3n+1) = A041047(5n+3), a(3n+2) = 2*A041047(5n+4). - Henry Bottomley, May 10 2000 a(n) = Sum_{alpha=RootOf(-1+5*z+z^2)} (1/29)*(5+2*alpha)*alpha^(-1-n). a(n-1) = (((5 + sqrt(29))/2)^n - ((5 - sqrt(29))/2)^n)/sqrt(29). - Gary W. Adamson, Jul 01 2003 a(n) = U(n, 5*i/2)*(-i)^n with i^2 = -1 and Chebyshev's U(n, x/2) = S(n, x) polynomials. See triangle A049310. Let M = {{0, 1}, {1, 5}}, then a(n) is the lower-right term of M^n. - Roger L. Bagula, May 29 2005 a(n) = F(n, 5), the n-th Fibonacci polynomial evaluated at x = 5. - T. D. Noe, Jan 19 2006 a(n) = denominator of n-th convergent to [1, 4, 5, 5, 5, ...], for n > 0. Continued fraction [1, 4, 5, 5, 5, ...] = 0.807417596..., the inradius of a right triangle with legs 2 and 5. n-th convergent = A100237(n)/A052918(n), the first few being: 1/1, 4/5, 21/26, 109/135, 566/701, ... - Gary W. Adamson, Dec 21 2007 From Johannes W. Meijer, Jun 12 2010: (Start) a(2n+1) = 5*A097781(n), a(2n) = A097835(n). Limit_{k->infinity} a(n+k)/a(k) = (A087130(n) + a(n-1)*sqrt(29))/2. Limit_{n->infinity} A087130(n)/a(n-1) = sqrt(29). (End) From L. Edson Jeffery, Jan 07 2012: (Start) Define the 2 X 2 matrix A = {{1, 1}, {5, 4}}. Then: a(n) is the upper-left term of (1/5)*(A^(n+2) - A^(n+1)); a(n) is the upper-right term of A^(n+1); a(n) is the lower-left term of (1/5)*A^(n+1); a(n) is the lower-right term of (Sum_{k=0..n} A^k). (End) Sum_{n>=0} (-1)^n/(a(n)*a(n+1)) = (sqrt(29) - 5)/2. - Vladimir Shevelev, Feb 23 2013 MAPLE spec := [S, {S=Sequence(Union(Z, Z, Z, Z, Z, Prod(Z, Z)))}, unlabeled]: seq(combstruct[count](spec, size=n), n=0..30); a:=1: a:=5: for n from 2 to 26 do a[n]:=5*a[n-1]+a[n-2] od: seq(a[n], n=0..30); # Zerinvary Lajos, Jul 26 2006 with(combinat):a:=n->fibonacci(n, 5):seq(a(n), n=1..30); # Zerinvary Lajos, Dec 07 2008 MATHEMATICA LinearRecurrence[{5, 1}, {1, 5}, 30] (* Vincenzo Librandi, Feb 23 2013 *) Table[Fibonacci[n+1, 5], {n, 0, 30}] (* Vladimir Reshetnikov, May 08 2016 *) PROG (Sage) [lucas_number1(n, 5, -1) for n in range(1, 22)] # Zerinvary Lajos, Apr 24 2009 (PARI) Vec(1/(1-5*x-x^2)+O(x^30)) \\ Charles R Greathouse IV, Nov 20 2011 (Magma) I:=[1, 5]; [n le 2 select I[n] else 5*Self(n-1)+Self(n-2): n in [1..30]]; // Vincenzo Librandi, Feb 23 2013 (Magma) R:=PowerSeriesRing(Integers(), 22); Coefficients(R!( 1/(1 - 5*x - x^2) )); // Marius A. Burtea, Oct 16 2019 (GAP) a:=[1, 5];; for n in [3..30] do a[n]:=5*a[n-1]+a[n-2]; od; a; # G. C. Greubel, Oct 16 2019 CROSSREFS Row 5 of A172236 (with an offset shift). Cf. A087130, A099365 (squares), A100237, A175184 (Pisano periods), A201005 (prime subsequence). Sequences with g.f. 1/(1-k*x-x^2) or x/(1-k*x-x^2): A000045 (k=1), A000129 (k=2), A006190 (k=3), A001076 (k=4), this sequence (k=5), A005668 (k=6), A054413 (k=7), A041025 (k=8), A099371 (k=9), A041041 (k=10), A049666 (k=11), A041061 (k=12), A140455 (k=13), A041085 (k=14), A154597 (k=15), A041113 (k=16), A178765 (k=17), A041145 (k=18), A243399 (k=19), A041181 (k=20). Sequence in context: A047768 A022032 A255118 * A255633 A255815 A018903 Adjacent sequences:  A052915 A052916 A052917 * A052919 A052920 A052921 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 2000 STATUS approved

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Last modified September 28 01:24 EDT 2022. Contains 357063 sequences. (Running on oeis4.)