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A028399 a(n) = 2^n - 4. 25
0, 4, 12, 28, 60, 124, 252, 508, 1020, 2044, 4092, 8188, 16380, 32764, 65532, 131068, 262140, 524284, 1048572, 2097148, 4194300, 8388604, 16777212, 33554428, 67108860, 134217724, 268435452, 536870908, 1073741820, 2147483644 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

Number of permutations of [n] with 2 sequences.

Number of 2 X n binary matrices that avoid simultaneously the right angled numbered polyomino patterns (ranpp) (00;1) and (11;0). An occurrence of a ranpp (xy;z) in a matrix A=(a(i,j)) is a triple (a(i1,j1), a(i1,j2), a(i2,j1)) where i1<i2, j1<j2 and these elements are in same relative order as those in the triple (x,y,z). - Sergey Kitaev (kitaev(AT)ms.uky.edu), Nov 11 2004

The number of edges in the dual Edwards-Venn diagram graph with n-1 digits when n>2.

REFERENCES

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 261.

A. W. F. Edwards, Cogwheels of the Mind, Johns Hopkins University Press, 2004, p. 82.

LINKS

Table of n, a(n) for n=2..31.

S. Kitaev, On multi-avoidance of right angled numbered polyomino patterns, Integers: Electronic Journal of Combinatorial Number Theory 4 (2004), A21, 20pp.

S. Kitaev, On multi-avoidance of right angled numbered polyomino patterns, University of Kentucky Research Reports (2004).

László Németh, Pascal pyramid in the space H^2 x R, arXiv:1701.06022 [math.CO], 2017 (3rd line of Table 2 is a(n+1)).

I. Strazdins, Universal affine classification of Boolean functions, Acta Applic. Math. 46 (1997), 147-167.

Index entries for linear recurrences with constant coefficients, signature (3,-2).

FORMULA

O.g.f.: 4x^3/((1-x)(1-2x)). [R. J. Mathar, Aug 07 2008]

From Reinhard Zumkeller, Feb 28 2010: (Start)

a(n) = A175164(2*n)/A140504(n+2);

a(2*n) = A052548(n)*A000918(n) for n>0;

a(n) = A173787(n,2). (End)

a(n) = a(n-1)+2^(n-1) (with a(2)=0). [Vincenzo Librandi, Nov 22 2010]

a(n) = 4*A000225(n-2). - R. J. Mathar, Dec 15 2015

PROG

(PARI) a(n)=if(n<2, 0, 2^n-4)

CROSSREFS

Sequence in context: A179023 A269712 * A173033 A034508 A173380 A002932

Adjacent sequences:  A028396 A028397 A028398 * A028400 A028401 A028402

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Additional comments from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Dec 02 2001

STATUS

approved

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Last modified October 22 02:43 EDT 2017. Contains 293756 sequences.