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A058682
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p(0)+p(1)+...+p(n-1)-n, where p = partition numbers, A000041.
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3
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0, 0, 1, 3, 7, 13, 23, 37, 58, 87, 128, 183, 259, 359, 493, 668, 898, 1194, 1578, 2067, 2693, 3484, 4485, 5739, 7313, 9270, 11705, 14714, 18431, 22995, 28598, 35439, 43787, 53929, 66238, 81120, 99096, 120732, 146746, 177930, 215267
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Number of non-isomorphic rank-2 matroids over S_n.
Starting (1, 3, 7, 13,...) = row sums of triangle A171239. [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Dec 05 2009]
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LINKS
| W. M. B. Dukes, Tables of matroids
W. M. B. Dukes, Counting and Probability in Matroid Theory, Ph.D. Thesis, Trinity College, Dublin, 2000.
Index entries for sequences related to matroids
W. M. B. Dukes, On the number of matroids on a finite set
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MAPLE
| a:=n->add(numbpart(k)-1, k=1..n-1): seq(a(n), n=1..41); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 01 2008
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CROSSREFS
| Cf. A000041, A000070. A diagonal of A053534.
Cf. A171239 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Dec 05 2009]
Sequence in context: A075321 A164787 A131205 * A081995 A053599 A136851
Adjacent sequences: A058679 A058680 A058681 * A058683 A058684 A058685
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Dec 30 2000
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