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 A056860 Triangle T(n,k) = number of element-subset partitions of {1..n} with n-k+1 equalities (n >= 1, 1 <= k <= n). 7
 1, 1, 1, 1, 2, 2, 1, 3, 6, 5, 1, 4, 12, 20, 15, 1, 5, 20, 50, 75, 52, 1, 6, 30, 100, 225, 312, 203, 1, 7, 42, 175, 525, 1092, 1421, 877, 1, 8, 56, 280, 1050, 2912, 5684, 7016, 4140, 1, 9, 72, 420, 1890, 6552, 17052, 31572, 37260, 21147 (list; table; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS T(n,k) = number of permutations on [n] with n in position k in which 321 patterns only occur as part of 3241 patterns. Example: T(4,2)=3 counts 1423, 2413, 3412. - David Callan, Jul 20 2005 From Gary W. Adamson, Feb 24 2011: (Start) Given rows of an array such that n-th row is the eigensequence of an infinite lower triangular matrix with first n columns of Pascal's triangle and the rest zeros. The reoriented finite differences of the array starting from the top are the rows of A056860. The first few rows of the array are   1,   1,   1,   1,   1,   1, ...   1,   2,   3,   4,   5,   6, ...   1,   2,   5,  10,  17,  26, ...   1,   2,   5,  15,  37,  76, ...   1,   2,   5,  15,  52, 151, ...   ... (End) REFERENCES W. C. Yang, Conjectures on some sequences involving set partitions and Bell numbers, preprint, 2000. LINKS David Callan, A Combinatorial Interpretation of the Eigensequence for Composition, Journal of Integer Sequences, Vol. 9 (2006), Article 06.1.4. FORMULA T(n, k) = binomial(n-1, k-1)*B(k-1) where B denotes the Bell numbers A000110. - David Callan, Jul 20 2005 EXAMPLE T(n,k) starts:   1;   1, 1;   1, 2,  2;   1, 3,  6,   5;   1, 4, 12,  20,   15;   1, 5, 20,  50,   75,   52;   1, 6, 30, 100,  225,  312,   203;   1, 7, 42, 175,  525, 1092,  1421,   877;   1, 8, 56, 280, 1050, 2912,  5684,  7016,  4140;   1, 9, 72, 420, 1890, 6552, 17052, 31572, 37260, 21147; Building row sums Sum_{c=1..k} T(n,c), the following array results:   1, 1,  1,   1,    1,    1,    1,     1,     1,     1, ...   1, 2,  2,   2,    2,    2,    2,     2,     2,     2, ...   1, 3,  5,   5,    5,    5,    5,     5,     5,     5, ...   1, 4, 10,  15,   15,   15,   15,    15,    15,    15, ...   1, 5, 17,  37,   52,   52,   52,    52,    52,    52, ...   1, 6, 26,  76,  151,  203,  203,   203,   203,   203, ...   1, 7, 37, 137,  362,  674,  877,   877,   877,   877, ...   1, 8, 50, 225,  750, 1842, 3263,  4140,  4140,  4140, ...   1, 9, 65, 345, 1395, 4307, 9991, 17007, 21147, 21147, ... CROSSREFS Essentially same as A056857, where rows are read from left to right. T(2n+1,n+1) gives A124102. T(2n,n) gives A297926. Sequence in context: A065173 A098474 A153199 * A158825 A247507 A107111 Adjacent sequences:  A056857 A056858 A056859 * A056861 A056862 A056863 KEYWORD nonn,tabl,easy AUTHOR N. J. A. Sloane, Oct 13 2000 EXTENSIONS More terms from David Callan, Jul 20 2005 STATUS approved

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Last modified December 10 18:10 EST 2019. Contains 329901 sequences. (Running on oeis4.)