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Search: id:A074092
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| A074092 |
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Number of plane binary trees of size n+3 and contracted height n. |
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+0
3
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| 1, 2, 8, 40, 144, 448, 1280, 3456, 8960, 22528, 55296, 133120, 315392, 737280, 1703936, 3899392, 8847360, 19922944, 44564480, 99090432, 219152384, 482344960, 1056964608, 2306867200, 5016387584, 10871635968, 23488102400
(list; graph; listen)
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OFFSET
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0,2
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LINKS
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H. Bottomley & A. Karttunen, Notes concerning diagonals of the square arrays A073345 and A073346.
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FORMULA
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a(0) = 1, a(1) = 2, a(n) = 2^(n-1)*(n+2)*(n-1) = (2^n)*(C(n, n-2)+C(n-1, n-2)) = 2^n * A000096(n-1).
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MAPLE
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A074092 := n -> `if`((n < 2), n+1, 2^(n-1)*(n+2)*(n-1));
A074092v2 := n -> `if`((n < 2), n+1, (2^n)*(binomial(n, n-2)+binomial(n-1, n-2)));
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CROSSREFS
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a(n) = A073346(n+3, n).
Sequence in context: A152458 A087971 A127919 this_sequence A003445 A071007 A027617
Adjacent sequences: A074089 A074090 A074091 this_sequence A074093 A074094 A074095
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KEYWORD
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nonn
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AUTHOR
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Antti Karttunen Aug 19 2002
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