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A104981
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Column 1 of triangle A104980; also equals column 0 of triangle A104986, which equals the matrix logarithm of A104980.
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7
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0, 1, 2, 7, 33, 191, 1297, 10063, 87669, 847015, 8989301, 103996703, 1303132269, 17589153719, 254509227541, 3931158238735, 64573130459613, 1124144767682215, 20677664894412965, 400760695386194687, 8163539437728923181
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OFFSET
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0,3
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LINKS
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FORMULA
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Let M = triangle A128175 as an infinite square production matrix (deleting the first "1"):
1, 1, 0, 0, 0, ...
2, 2, 1, 0, 0, ...
4, 4, 3, 1, 0, ...
8, 8, 7, 4, 1, ...
...
a(n) = sum of top row terms of M^(n-1). Example: top row of M^4 = (71, 71, 38, 10, 1), sum = 191 = a(5). (End)
a(0) = 1, a(n) = n * a(n-1) + Sum_{j=1..n} A003319(j) * a(n - j), with offset 0 for the term 1. - F. Chapoton, Feb 26 2018
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MATHEMATICA
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T[n_, k_]:= T[n, k]= If[n<k || k<0, 0, If[n==k, 1, If[n==k+1, n, k*T[n, k+1] + Sum[T[j, 0]*T[n, j+k+1], {j, 0, n-k-1}]]]];
a[n_]:= T[n, 1];
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PROG
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(PARI) {a(n) = if(n<0, 0, (matrix(n+2, n+2, m, j, if(m==j, 1, if(m==j+1, -m+1, -polcoeff((1-1/sum(i=0, m, i!*x^i))/x +O(x^m), m-j-1))))^-1)[n+1, 2])}
(Sage)
@CachedFunction
def T(n, k):
if (k<0 or k>n): return 0
elif (k==n): return 1
elif (k==n-1): return n
else: return k*T(n, k+1) + sum( T(j, 0)*T(n, j+k+1) for j in (0..n-k-1) )
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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