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Search: id:A101819
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| A101819 |
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Triangle read by rows: T(n,h) = number of functions f:{1,2,...,n}->{1,2,...,n-1} such that |Image(f)|=h, h=1,2,...,n-1, n=2,3,... |
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+0
5
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| 1, 2, 6, 3, 42, 36, 4, 180, 600, 240, 5, 620, 5400, 7800, 1800, 6, 1890, 36120, 12600, 100800, 15120, 7, 5334, 202860, 1428840, 2646000, 1340640, 141120, 8, 14280, 1016400, 13053600, 46710720, 53343360, 18627840, 1451520, 9, 36792, 4702320
(list; table; graph; listen)
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OFFSET
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0,2
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FORMULA
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T(n, h) = C(n-1, h)*U(n, h), where U(n, h) is the array in A019538.
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EXAMPLE
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First rows:
1
2 6
3 42 36
4 180 600 240
To see that T(4,2)=42, first count 7 functions from {1,2,3,4}
onto {1,2} with f(1)=1, and 7 with f(1)=2. Count 14 onto {1,3}
and 14 onto {2,3}, for a total of 42.
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CROSSREFS
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Cf. A019538, A101817, A101819, A101821.
Sequence in context: A144362 A125666 A111678 this_sequence A128192 A077750 A076393
Adjacent sequences: A101816 A101817 A101818 this_sequence A101820 A101821 A101822
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KEYWORD
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nonn,tabl
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu), Dec 17 2004
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