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A162515 Triangle of coefficients of polynomials defined by Binet form: P(n,x) = (U^n - L^n)/d, where U = (x + d)/2, L = (x - d)/2, d = sqrt(x^2 + 4). 6

%I

%S 0,1,1,0,1,0,1,1,0,2,0,1,0,3,0,1,1,0,4,0,3,0,1,0,5,0,6,0,1,1,0,6,0,10,

%T 0,4,0,1,0,7,0,15,0,10,0,1,1,0,8,0,21,0,20,0,5,0,1,0,9,0,28,0,35,0,15,

%U 0,1,1,0,10,0,36,0,56,0,35,0,6,0,1,0,11,0,45,0,84,0,70,0,21,0,1

%N Triangle of coefficients of polynomials defined by Binet form: P(n,x) = (U^n - L^n)/d, where U = (x + d)/2, L = (x - d)/2, d = sqrt(x^2 + 4).

%C Row sums 0,1,1,2,3,5,... are the Fibonacci numbers, A000045.

%C Note that the coefficients are given in decreasing order. - _M. F. Hasler_, Dec 07 2011

%C Essentially a mirror image of A168561. - _Philippe Deléham_, Dec 08 2013

%H G. C. Greubel, <a href="/A162515/b162515.txt">Rows n = 0..101 of triangle</a>

%H T. Copeland, <a href="https://tcjpn.wordpress.com/2015/10/12/the-elliptic-lie-triad-kdv-and-ricattt-equations-infinigens-and-elliptic-genera/">Addendum to Elliptic Lie Triad</a>

%F P(n,x) = x*P(n-1, x) + P(n-2, x), where P(0,x)=0 and P(1,x)=1.

%F T(n,k) = T(n-1, k) + T(n-2, k-2) for n>=2. - _Philippe Deléham_, Dec 08 2013

%e Polynomial expansion:

%e 0;

%e 1;

%e x;

%e x^2 + 1;

%e x^3 + 2*x;

%e x^4 + 3*x^2 + 1;

%e First rows:

%e 0;

%e 1;

%e 1, 0;

%e 1, 0, 1;

%e 1, 0, 2, 0;

%e 1, 0, 3, 0, 1;

%e 1, 0, 4, 0, 3, 0;

%e Row 6 matches P(6,x)=x^5 + 4*x^3 + 3*x.

%p 0, seq(seq(`if`(`mod`(k,2)=0, binomial(n-k/2, k/2), 0), k = 0..n), n = 0..15); # _G. C. Greubel_, Jan 01 2020

%t Join[{0}, Table[If[EvenQ[k], Binomial[n-k/2, k/2], 0], {n,0,15}, {k,0,n} ]//Flatten] (* _G. C. Greubel_, Jan 01 2020 *)

%o (PARI) P(n) = my( d=(4 + x^2)^(1/2), U=(x+d)/2, L=(x-d)/2); Vec(Pol((U^n-L^n)/d)) \\ _M. F. Hasler_, Dec 07 2011

%o (MAGMA)

%o function T(n,k)

%o if (k mod 2) eq 0 then return Round( Gamma(n-k/2+1)/(Gamma(k/2+1)*Gamma(n-k+1)));

%o else return 0;

%o end if; return T; end function;

%o [0] cat [T(n,k): k in [0..n], n in [0..15]]; // _G. C. Greubel_, Jan 01 2020

%o (Sage)

%o @CachedFunction

%o def T(n, k):

%o if (k%2==0): return binomial(n-k/2, k/2)

%o else: return 0

%o [0]+flatten([[T(n, k) for k in (0..n)] for n in (0..15)]) # _G. C. Greubel_, Jan 01 2020

%o (GAP)

%o T:= function(n,k)

%o if (k mod 2)=0 then return Binomial(n- k/2, k/2);

%o else return 0;

%o fi; end;

%o Concatenation([0], Flat(List([0..15], n-> List([0..n], k-> T(n,k) ))) ); # _G. C. Greubel_, Jan 01 2020

%Y Cf. A000045, A049310, A053119, A162514, A162516, A162517.

%K nonn,tabf

%O 0,10

%A _Clark Kimberling_, Jul 05 2009

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Last modified August 10 16:56 EDT 2020. Contains 336381 sequences. (Running on oeis4.)