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 A124295 Number of free generators of degree n of symmetric polynomials in 7-noncommuting variables. 4
 1, 1, 2, 6, 22, 92, 426, 2145, 11589, 66425, 399682, 2500037, 16115347, 106266473, 712602272, 4837372576, 33128183406, 228308233098, 1580495251012, 10976092266889, 76398165848091, 532614662149795, 3717370694711130 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS Also the number of non-splitable set partitions (see Bergeron et al. reference) of length <=7 REFERENCES M. C. Wolf, Symmetric functions of noncommutative elements, Duke Math. J. 2 (1936), 626-637. LINKS N. Bergeron, C. Reutenauer, M. Rosas and M. Zabrocki, Invariants and Coinvariants of the Symmetric Group in Noncommuting Variables, arXiv:math.CO/0502082 , Canad. J. Math. 60 (2008), no. 2, 266-296. FORMULA O.g.f.: (1-20*q+151*q^2-535*q^3+881*q^4-531*q^5) / (1-21*q+170*q^2 -669*q^3 +1314*q^4-1157*q^5+309*q^6) = (1 - 1/(sum_{k=0}^7 q^k/(prod_{i=1}^k (1-i*q))))/q a(n) = add( A055105(n,k), k=1..7) = add(A055106(n,k), k=1..6). CROSSREFS Cf. A055105, A055106, A055107, A074664, A001519, A124292, A124293, A124294. Sequence in context: A014330 A225294 A124294 * A074664 A091768 A229741 Adjacent sequences:  A124292 A124293 A124294 * A124296 A124297 A124298 KEYWORD nonn AUTHOR Mike Zabrocki, Oct 24 2006 STATUS approved

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