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A008299
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Triangle of associated Stirling numbers of second kind.
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19
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1, 1, 1, 3, 1, 10, 1, 25, 15, 1, 56, 105, 1, 119, 490, 105, 1, 246, 1918, 1260, 1, 501, 6825, 9450, 945, 1, 1012, 22935, 56980, 17325, 1, 2035, 74316, 302995, 190575, 10395, 1, 4082, 235092, 1487200, 1636635, 270270, 1, 8177, 731731, 6914908, 12122110
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OFFSET
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2,4
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COMMENTS
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T(n,k) is the number of set partitions of [n] into k blocks of size at least 2. Compare with A008277 (blocks of size at least 1) and A059022 (blocks of size at least 3). See also A200091. Reading the table by diagonals gives A134991. The row generating polynomials are the Mahler polynomials s_n(-x). See [Roman, 4.9]. Rows are of lengths 1,1,2,2,3,3,....
For a relation to decomposition of spin correlators see Table 2 of the Delfino and Vito paper. - Tom Copeland, Nov 11 2012
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REFERENCES
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L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 222.
A. E. Fekete, Apropos two notes on notation, Amer. Math. Monthly, 101 (1994), 771-778.
J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 76.
S. Roman, The Umbral Calculus, Dover Publications, New York (2005), pp. 129-130.
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LINKS
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Vincenzo Librandi and Alois P. Heinz, Rows n = 2..200, flattened (rows n = 2..104 from Vincenzo Librandi)
P. Bala, Diagonals of triangles with generating function exp(t*F(x)).
J. Fernando Barbero G., Jesús Salas, Eduardo J. S. Villaseñor, Bivariate Generating Functions for a Class of Linear Recurrences. I. General Structure, arXiv:1307.2010, 2013
Gesualdo Delfino and Jacopo Viti, Potts q-color field theory and scaling random cluster model, arXiv:1104.4323, 2011.
L. M. Smiley, Completion of a Rational Function Sequence of Carlitz
Eric Weisstein's World of Mathematics, Mahler polynomial
Wikipedia, Mahler polynomials
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FORMULA
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E.g.f. with additional constant 1: exp(t*(exp(x)-1-x)) = 1+t*x^2/2!+t*x^3/3!+(t+3*t^2)*x^4/4!+....
Recurrence relation: T(n+1,k) = k*T(n,k) + n*T(n-1,k-1).
T(n,k) = A134991(n-k,k); A134991(n,k) = T(n+k,k).
More generally, if S_r(n,k) counts the number of set partitions of [n] into k blocks of size at least r then we have the recurrence S_r(n+1,k)=k*S_r(n,k)+binomial(n,r-1)*S_r(n-r+1,k-1) (for this sequence, r=2), with associated e.g.f.: sum(S_r(n,k)*u^k*(t^n/n!), n=0..infty, k=0..infty)=exp(u*(e^t-sum(t^i/i!, i=0..r-1))).
T(n,k) = sum_{i=0..k} (-1)^i*binomial(n, i)*[sum_{j=0..k-i} (-1)^j*(k -i -j)^(n-i)/(j!*(k-i-j)!)] - David Wasserman, Jun 13 2007
G.f.: (R(0)-1)/(x^2*y), where R(k) = 1 - (k+1)*y*x^2/( (k+1)*y*x^2 -(1- k*x)*(1-x - k*x)/R(k+1) ); (continued fraction). - Sergei N. Gladkovskii, Nov 09 2013
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EXAMPLE
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There are 3 ways of partitioning a set N of cardinality 4 into 2 blocks each of cardinality at least 2, so S_2(4,2)=3. Table begins
.n\k.|..1....2.....3.....4
= = = = = = = = = = = = = =
..2..|..1
..3..|..1
..4..|..1....3
..5..|..1...10
..6..|..1...25....15
..7..|..1...56...105
..8..|..1..119...490...105
..9..|..1..246..1918..1260
...
Reading the table by diagonals produces the triangle A134991.
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MATHEMATICA
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t[n_, k_] := Sum[ (-1)^i*Binomial[n, i]*Sum[ (-1)^j*(k - i - j)^(n - i)/(j!*(k - i - j)!), {j, 0, k - i}], {i, 0, k}]; Flatten[ Table[ t[n, k], {n, 2, 14}, {k, 1, Floor[n/2]}]] (* Jean-François Alcover, Oct 13 2011, after David Wasserman *)
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PROG
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(PARI) {T(n, k) = if( n < 1 || 2*k > n, n==0 && k==0, sum(i=0, k, (-1)^i * binomial( n, i) * sum(j=0, k-i, (-1)^j * (k-i-j)^(n-i) / (j! * (k-i-j)!))))}; /* Michael Somos, Oct 19 2014 */
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CROSSREFS
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Rows give A000247, A000478, A058844.
Cf. A059022, A059023, A059024, A059025.
Row sums: A000296. A134991. A200091.
Sequence in context: A211360 A178866 A019427 * A016478 A102430 A135573
Adjacent sequences: A008296 A008297 A008298 * A008300 A008301 A008302
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KEYWORD
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nonn,tabf,nice
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AUTHOR
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N. J. A. Sloane.
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EXTENSIONS
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Formula and cross-references from Barbara Haas Margolius (margolius(AT)math.csuohio.edu), Dec 14 2000
More terms from David Wasserman, Jun 13 2007
Edited by Peter Bala, Dec 04 2011
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STATUS
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approved
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