

A129639


Number of meaningful differential operations of the kth order on the space R^12.


4



12, 22, 40, 74, 136, 252, 464, 860, 1584, 2936, 5408, 10024, 18464, 34224, 63040, 116848, 215232, 398944, 734848, 1362080, 2508928, 4650432, 8566016, 15877568, 29246208, 54209408, 99852800, 185082496, 340918784, 631911168, 1163969536
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OFFSET

12,1


COMMENTS

Also (starting 7,12,...) the number of zigzag paths from top to bottom of a rectangle of width 7. [Joseph Myers, Dec 23 2008]


LINKS

Table of n, a(n) for n=12..42.
B. Malesevic, Some combinatorial aspects of differential operation composition on the space R^n, Univ. Beograd, Publ. Elektrotehn. Fak., Ser. Mat. 9 (1998), 2933.
Branko Malesevic, Some combinatorial aspects of differential operation compositions on space R^n, arXiv:0704.0750 [math.DG], 2007.
Joseph Myers, BMO 20082009 Round 1 Problem 1Generalisation


FORMULA

f(k+6) = 6*f(k+4)10*f(k+2)+4*f(k).
Empirical G.f.: 2*x^12*(6+11*x4*x^27*x^3)/(14*x^2+2*x^4). [Colin Barker, May 07 2012]


MAPLE

NUM := proc(k :: integer) local i, j, n, Fun, Identity, v, A; n:=12; # < DIMENSION Fun:=(i, j)>piecewise(((j=i+1) or (i+j=n+1)), 1, 0); Identity:=(i, j)>piecewise(i=j, 1, 0); v:=matrix(1, n, 1); A:=piecewise(k>1, (matrix(n, n, Fun))^(k1), k=1, matrix(n, n, Identity)); return(evalm(v&*A&*transpose(v))[1, 1]); end:


CROSSREFS

Cf. A090989A090995.
Sequence in context: A285470 A124885 A115745 * A153361 A200197 A115709
Adjacent sequences: A129636 A129637 A129638 * A129640 A129641 A129642


KEYWORD

nonn


AUTHOR

Branko Malesevic, May 31 2007


EXTENSIONS

More terms from Joseph Myers, Dec 23 2008


STATUS

approved



