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 A006357 Number of distributive lattices; also number of paths with n turns when light is reflected from 4 glass plates. (Formerly M3396) 14
 1, 4, 10, 30, 85, 246, 707, 2037, 5864, 16886, 48620, 139997, 403104, 1160693, 3342081, 9623140, 27708726, 79784098, 229729153, 661478734, 1904652103, 5484227157, 15791202736, 45468956106, 130922641160, 376976720745, 1085461206128, 3125460977225 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Let M denotes the 4 X 4 matrix = row by row (1,1,1,1)(1,1,1,0)(1,1,0,0)(1,0,0,0) and A(n) the vector (x(n),y(n),z(n),t(n))=M^n*A where A is the vector (1,1,1,1) then a(n)=x(n). - Benoit Cloitre, Apr 02 2002 In general, the g.f. for p glass plates is A(x) = F_{p-1}(-x)/F_p(x) where F_p(x) = Sum_{k=0,p} (-1)^[(k+1)/2]*C([(p+k)/2],k)*x^k. - Paul D. Hanna, Feb 06 2006 a(n)/a(n-1) tends to 2.879385..., the longest diagonal of a nonagon with edge 1; or: sin(4*Pi/9)/sin(Pi/9). The sequence is the INVERT transform of (1, 3, 3, 5, 8, 13, 21, 34, 55, 89, 144, ...). - Gary W. Adamson, Jul 16 2015 REFERENCES J. Berman and P. Koehler, Cardinalities of finite distributive lattices, Mitteilungen aus dem Mathematischen Seminar Giessen, 121 (1976), 103-124. S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (see p. 120). J. Haubrich, Multinacci Rijen [Multinacci sequences], Euclides (Netherlands), Vol. 74, Issue 4, 1998, pp. 131-133. N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS T. D. Noe, Table of n, a(n) for n = 0..200 J. Berman and P. Koehler, Cardinalities of finite distributive lattices, Mitteilungen aus dem Mathematischen Seminar Giessen, 121 (1976), 103-124. [Annotated scanned copy] Emma L. L. Gao, Sergey Kitaev, Philip B. Zhang, Pattern-avoiding alternating words, preprint, 2015. Manfred Goebel, Rewriting Techniques and Degree Bounds for Higher Order Symmetric Polynomials, Applicable Algebra in Engineering, Communication and Computing (AAECC), Volume 9, Issue 6 (1999), 559-573. G. Kreweras, Les préordres totaux compatibles avec un ordre partiel, Math. Sci. Humaines No. 53 (1976), 5-30. G. Kreweras, Les préordres totaux compatibles avec un ordre partiel, Math. Sci. Humaines No. 53 (1976), 5-30. (Annotated scanned copy) Simon Plouffe, Approximations de séries génératrices et quelques conjectures, Dissertation, Université du Québec à Montréal, 1992. Simon Plouffe, 1031 Generating Functions and Conjectures, Université du Québec à Montréal, 1992. Index entries for linear recurrences with constant coefficients, signature (2,3,-1,-1). FORMULA a(n) = 2*a(n-1) + 3*a(n-2) - a(n-3) - a(n-4). a(n) is asymptotic to z(4)*w(4)^n where w(4) = (1/2)/cos(4*Pi/9) and z(4) is the root 1 < x < 2 of P(4, X) = 1 + 27*X - 324*X^2 + 243*X^3. - Benoit Cloitre, Oct 16 2002 G.f.: A(x) = (1 + 2*x - x^2 - x^3)/(1 - 2*x - 3*x^2 + x^3 + x^4). - Paul D. Hanna, Feb 06 2006 Binomial transform of A122167(unsigned): (1, 3, 3, 11, 10, 40, 33, 146, ...). - Gary W. Adamson, Nov 24 2007 G.f.: 1/(-x-1/(-x-1/(-x-1/(-x-1)))). - Paul Barry, Mar 24 2010 MAPLE A006357:=-(-1+z**2-2*z+z**3)/(1+z)/(z**3-3*z+1); # conjectured by Simon Plouffe in his 1992 dissertation MATHEMATICA LinearRecurrence[{2, 3, -1, -1}, {1, 4, 10, 30}, 30] (* Harvey P. Dale, Nov 18 2013 *) PROG (PARI) a(n)=local(p=4); polcoeff(sum(k=0, p-1, (-1)^((k+1)\2)*binomial((p+k-1)\2, k)* (-x)^k)/sum(k=0, p, (-1)^((k+1)\2)*binomial((p+k)\2, k)*x^k+x*O(x^n)), n) \\ Paul D. Hanna CROSSREFS Cf. A000217, A000330, A050446, A050447, A006356-A006359, A025030, A030112-A030116, A122167, A091024. Cf. A038197 (4-wave sequence). Sequence in context: A007713 A058488 A036674 * A047088 A114946 A243793 Adjacent sequences:  A006354 A006355 A006356 * A006358 A006359 A006360 KEYWORD nonn,nice,easy AUTHOR EXTENSIONS Recurrence, alternative description from Jacques Haubrich (jhaubrich(AT)freeler.nl) More terms from James A. Sellers, Dec 24 1999 More terms from Paul D. Hanna, Feb 06 2006 STATUS approved

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Last modified October 15 12:31 EDT 2019. Contains 328026 sequences. (Running on oeis4.)