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A245731
Number of connected labeled transitive relations on an n-set.
2
1, 2, 9, 109, 2647, 110481, 7291543, 726434549, 106312974249, 22465350835849, 6771847676632679, 2883916106465622053, 1720792953946798909927, 1427968172285571102335605, 1637002867699829205840095585, 2577011453377960519672777065693, 5541005747990556022043234479371823, 16195114271558690956785525865003941945, 64068293759315414337050896928055465961863
OFFSET
0,2
FORMULA
E.g.f.: log(A(x + exp(x) - 1)) + 1 where A(x) is the e.g.f. for A001035.
EXAMPLE
a(2) = 9. There are 13 transitive relations on the set {1,2}. Four of these are not connected: {}, {(1,1)}, {(2,2)}, {(1,1),(2,2)}. 13-4=9.
CROSSREFS
Sequence in context: A309452 A354663 A219116 * A290714 A062498 A339015
KEYWORD
nonn
AUTHOR
Geoffrey Critzer, Jul 30 2014
STATUS
approved