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A179199
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E.g.f. satisfies: A(x) = (1+x)/(1+2*x)*A(x+x^2) with A(0)=0.
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3
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0, 1, -2, 9, -64, 620, -7536, 109032, -1809984, 33562944, -681799680, 14980204800, -354016189440, 9017296704000, -249422713344000, 7530733353024000, -246212297533440000, 8509848430274150400, -302719894872204902400
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OFFSET
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0,3
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LINKS
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G. C. Greubel, Table of n, a(n) for n = 0..300
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FORMULA
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E.g.f. A=A(x) satisfies: x = A + A*Dx(A)/2! + A*Dx(A*Dx(A))/3! + A*Dx(A*Dx(A*Dx(A)))/4! + ... where Dx(F) = d/dx(x*F).
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a(n) = -n*(n-2)!*Sum_{i=1..n-1} C(n-i+1,i+1)*a(n-i)/(n-i)! for n>1 with a(1)=1.
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a(n) = (-1)^(n-1)*n*A005119(n), where A005119 describes the infinitesimal generator of (x+x^2).
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Equals column 0 of A179198, the matrix log of triangle A030528, where A030528(n,k) = C(k,n-k); the g.f. of column k in A030528 is (x+x^2)^(k+1)/x.
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A179198(n,k) = (k+1)*a(n-k)/(n-1)! for n>0, k>=0, where A179198 = matrix log of triangle A030528.
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EXAMPLE
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E.g.f.: A(x) = x - 2*x^2/2! + 9*x^3/3! - 64*x^4/4! + 620*x^5/5! - 7536*x^6/6! + 109032*x^7/7! - 1809984*x^8/8! + 33562944*x^9/9! - 681799680*x^10/10! + 14980204800*x^11/11! - 354016189440*x^12/12! + ...
E.g.f. satisfies: A(x) = (1+x)/(1+2*x)*A(x+x^2) where:
. A(x+x^2) = x - 3*x^3/3! + 20*x^4/4! - 120*x^5/5! + 624*x^6/6! - 840*x^7/7! - 58752*x^8/8! + 1512000*x^9/9! - 25660800*x^10/10! + ...
E.g.f. A = A(x) satisfies:
. x = A + A*Dx(A)/2! + A*Dx(A*Dx(A))/3! + A*Dx(A*Dx(A*Dx(A)))/4! + ...
where Dx(F) = d/dx(x*F) and expansions begin:
. A*Dx(A) = 4*x^2/2! - 30*x^3/3! + 288*x^4/4! - 3500*x^5/5! +- ...
. A*Dx(A*Dx(A)) = 36*x^3/3! - 624*x^4/4! + 10680*x^5/5! -+ ...
. A*Dx(A*Dx(A*Dx(A))) = 576*x^4/4! - 18480*x^5/5! + 504000*x^6/6! -+ ...
. A*Dx(A*Dx(A*Dx(A*Dx(A)))) = 14400*x^5/5! - 751680*x^6/6! +- ...
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MATHEMATICA
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a[n_]:= a[n]= If[n<2, n, (-1/(n-1))*Sum[j!*Binomial[n, j]*Binomial[n-j+1, j+1]*a[n -j], {j, n-1}]];
Table[a[n], {n, 0, 40}] (* G. C. Greubel, Sep 03 2022 *)
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PROG
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(PARI) /* E.g.f. satisfies: A(x) = (1+x)/(1+2*x)*A(x+x^2): */
{a(n)=local(A=x, B); for(m=2, n, B=(1+x)/(1+2*x+O(x^(n+3)))*subst(A, x, x+x^2+O(x^(n+3))); A=A-polcoeff(B, m+1)*x^m/(m-1)); n!*polcoeff(A, n)}
(PARI) /* Recurrence (slow): */
{a(n)=if(n<1, 0, if(n==1, 1, -n*(n-2)!*sum(i=1, n-1, binomial(n-i+1, i+1)*a(n-i)/(n-i)!)))}
(PARI) /* x = A + A*Dx(A)/2! + A*Dx(A*Dx(A))/3! + A*Dx(A*Dx(A*Dx(A)))/4! +...: */
{a(n)=local(A=x+sum(m=2, n-1, a(m)*x^m/m!), G=1, R=0); R=sum(m=1, n, (G=A*deriv(x*G+x*O(x^n)))/m!); if(n==1, 1, -n!*polcoeff(R, n))}
(PARI) /* As column 0 of the matrix log of triangle A030528: */
{a(n)=local(A030528=matrix(n+1, n+1, r, c, if(r>=c, binomial(c, r-c))), LOG, ID=A030528^0); LOG=sum(m=1, n+1, -(ID-A030528)^m/m); n!*LOG[n+1, 1]}
(SageMath)
@CachedFunction
def a(n): # a = A179199
if (n<2): return n
else: return (-1/(n-1))*sum( factorial(j)*binomial(n, j)*binomial(n-j+1, j+1)*a(n-j) for j in (1..n-1) )
[a(n) for n in (0..40)] # G. C. Greubel, Sep 03 2022
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CROSSREFS
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Cf. A005119, A030528, A179198.
Sequence in context: A269683 A331658 A269487 * A036775 A141209 A269770
Adjacent sequences: A179196 A179197 A179198 * A179200 A179201 A179202
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KEYWORD
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eigen,sign
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AUTHOR
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Paul D. Hanna, Jul 09 2010
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STATUS
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approved
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