A187107 - OEIS

%I #29 Oct 21 2017 21:01:39

%S 8,8,9,10,12,15,20,28,41,62,96,151,240,384,617,994,1604,2591,4188,

%T 6772,10953,17718,28664,46375,75032,121400,196425,317818,514236,

%U 832047,1346276,2178316,3524585,5702894,9227472,14930359,24157824,39088176

%N Number of nontrivial compositions of differential operations and directional derivative of the n-th order on the space R^9.

%H Ivana Jovović and Branko Malešević, <a href="http://nntdm.net/volume-23-2017/number-1/28-38/">Some enumerations of non-trivial composition of the differential operations and the directional derivative</a>, Notes on Number Theory and Discrete Mathematics, Vol. 23, 2017, No. 1, 28-38.

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,0,-1).

%F a(n) = A000045(n) + 7.

%F a(n) = 2*a(n-1)-a(n-3). G.f.: -x*(7*x^2+8*x-8) / ((x-1)*(x^2+x-1)). [_Colin Barker_, Dec 14 2012]

%t LinearRecurrence[{2,0,-1},{8,8,9},50] (* _Harvey P. Dale_, Jul 10 2017 *)

%Y Cf. A000045.

%K nonn,easy

%O 1,1

%A _Branko Malesevic_, Mar 06 2011