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A001789
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a(n) = binomial(n,3)*2^(n-3).
(Formerly M4522 N1916)
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33
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1, 8, 40, 160, 560, 1792, 5376, 15360, 42240, 112640, 292864, 745472, 1863680, 4587520, 11141120, 26738688, 63504384, 149422080, 348651520, 807403520, 1857028096, 4244635648, 9646899200, 21810380800, 49073356800, 109924319232
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OFFSET
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3,2
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COMMENTS
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Number of 3-dimensional cubes in n-dimensional hypercube. - Henry Bottomley, Apr 14 2000
With three leading zeros, this is the second binomial transform of (0,0,0,1,0,0,0,0,...). - Paul Barry, Mar 07 2003
With 3 leading zeros, binomial transform of C(n,3). - Paul Barry, Apr 10 2003
Let M=[1,0,i;0,1,0;i,0,1], i=sqrt(-1). Then 1/det(I-xM)=1/(1-2x)^4. - Paul Barry, Apr 27 2005
If X_1,X_2,...,X_n is a partition of a 2n-set X into 2-blocks then, for n>2, a(n+1) is equal to the number of (n+3)-subsets of X intersecting each X_i (i=1,2,...,n). - Milan Janjic, Jul 21 2007
With offset 0, a(n) is the number of ways to separate [n] into four non-overlapping intervals (allowed to be empty) and then choose a subset from each interval. - Geoffrey Critzer, Feb 07 2009
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REFERENCES
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M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 796.
Clifford A. Pickover, The Math Book, From Pythagoras to the 57th Dimension, 250 Milestones in the History of Mathematics, Sterling Publ., NY, 2009, page 282.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
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M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
C. W. Jones, J. C. P. Miller, J. F. C. Conn and R. C. Pankhurst, Tables of Chebyshev polynomials Proc. Roy. Soc. Edinburgh. Sect. A., Vol. 62, No. 2 (1946), pp. 187-203.
Eric Weisstein's World of Mathematics, Hypercube.
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FORMULA
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G.f. (with three leading zeros): x^3/(1-2*x)^4.
With three leading zeros, a(n) = 8*a(n-1) - 24*a(n-2) + 32*a(n-3) - 16*a(n-4), a(0)=a(1)=a(2)=0, a(3)=1.
E.g.f.: (x^3/3!)*exp(2*x) (with 3 leading zeros). (End)
a(n) = Sum_{i=3..n} binomial(i,3)*binomial(n,i). Example: for n=6, a(6) = 1*20 + 4*15 + 10*6 + 20*1 = 160. - Bruno Berselli, Mar 23 2018
Sum_{n>=3} 1/a(n) = 6*log(2) - 3.
Sum_{n>=3} (-1)^(n+1)/a(n) = 54*log(3/2) - 21. (End)
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MAPLE
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MATHEMATICA
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LinearRecurrence[{8, -24, 32, -16}, {1, 8, 40, 160}, 30] (* Harvey P. Dale, Feb 10 2016 *)
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PROG
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(Haskell)
a001789 n = a007318 n 3 * 2 ^ (n - 3)
a001789_list = 1 : zipWith (+) (map (* 2) a001789_list) (drop 2 a001788_list)
(Magma) [Binomial(n, 3)*2^(n-3): n in [3..30]]; // G. C. Greubel, Aug 27 2019
(GAP) List([3..30], n-> Binomial(n, 3)*2^(n-3)); # G. C. Greubel, Aug 27 2019
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CROSSREFS
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KEYWORD
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nonn,easy,nice
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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