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Search: id:A001697
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| A001697 |
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a(n+1)=a(n)(a(0)+ ... +a(n)).
(Formerly M1902 N0751)
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+0
4
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| 1, 1, 2, 8, 96, 10368, 108615168, 11798392572168192, 139202068568601556987554268864512, 19377215893777651167043206536157390321290709180447278572301746176
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Number of binary trees of height n where for each node the left subtree is at least as high as the right subtree. - Franklin T. Adams-Watters, Feb 08 2007
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LINKS
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A. V. Aho and N. J. A. Sloane, Some doubly exponential sequences, Fib. Quart., 11 (1973), 429-437.
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PROGRAM
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(PARI) a(n)=if(n<2, n >= 0, a(n-1)^2*(1+1/a(n-2)))
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CROSSREFS
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a(n)=A039941(2*n+1); first difference sequence of A001696 is this sequence.
Cf. A002658, A001699.
Adjacent sequences: A001694 A001695 A001696 this_sequence A001698 A001699 A001700
Sequence in context: A009752 A137704 A001417 this_sequence A006069 A052457 A119654
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KEYWORD
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nonn,easy,nice
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AUTHOR
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njas
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EXTENSIONS
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Additional comments from Michael Somos, May 19, 2000
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