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A109516 a(n) is the (1,2)-entry of the n-th power of the 2 X 2 matrix [0,1;n-1,n-1]. 0

%I

%S 1,1,6,45,464,6000,93528,1707111,35721216,843160671,22165100000,

%T 642268811184,20339749638144,698946255836933,25903663544572800,

%U 1029945249481640625,43733528272753917952,1975222567881226040760

%N a(n) is the (1,2)-entry of the n-th power of the 2 X 2 matrix [0,1;n-1,n-1].

%C The (1,2)-entry of the n-th power of the 2 X 2 matrix [0,1;1,1] is the Fibonacci number A000045(n).

%F a(n) = [x^n] 1/(1 - n*x - n*x^2). - _Paul D. Hanna_, Dec 27 2012

%F a(n+1) = Sum_{k=0..floor(n/2)} binomial(n-k,k)*n^(n-k) for n>=0 (conjectured). - _Werner Schulte_, Oct 21 2016

%F a(n) = ((n + sqrt((n-1)*(n+3)) - 1)^n - (n - sqrt((n-1)*(n+3)) - 1)^n) / (2^n * sqrt((n-1)*(n+3))), for n > 1. - _Daniel Suteu_, Apr 20 2018

%F a(n) ~ n^(n-1). - _Vaclav Kotesovec_, Apr 20 2018

%e a(4)=45 because if M is the 2 X 2 matrix [0,1;3,3], then M^4 is the 2 X 2 matrix [36,45;135;171].

%e G.f. = x + x^2 + 6*x^3 + 45*x^4 + 464*x^5 + 6000*x^6 + 93528*x^7 + 1707111*x^8 + ...

%p with(linalg): a:=proc(n) local A,k: A[1]:=matrix(2,2,[0,1,n-1,n-1]): for k from 2 to n do A[k]:=multiply(A[k-1],A[1]) od: A[n][1,2] end: seq(a(n),n=1..20);

%t M[n_] = If[n > 1, MatrixPower[{{0, 1}, {n - 1, n - 1}}, n], {{0, 1}, {1, 1}}]; a = Table[M[n][[1, 2]], {n, 1, 50}]

%t Table[SeriesCoefficient[1/(1 - n*x - n*x^2), {x,0,n}], {n,0,20}] (* _Vaclav Kotesovec_, Apr 20 2018 *)

%o (PARI) {a(n)=polcoeff(1/(1-n*x-n*x^2+x*O(x^n)), n)} \\ _Paul D. Hanna_, Dec 27 2012

%o (PARI) a(n) = ([0,1;n-1,n-1]^n)[1, 2]; \\ _Michel Marcus_, Apr 20 2018

%Y Cf. A000045, A000166.

%K nonn

%O 1,3

%A _Roger L. Bagula_, Jun 16 2005

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Last modified July 18 08:22 EDT 2018. Contains 312735 sequences. (Running on oeis4.)