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Search: id:A117718
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| A117718 |
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Number of heptagonal numbers with n digits. |
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+0
1
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| 3, 4, 14, 43, 137, 432, 1368, 4324, 13676, 43245, 136755, 432455, 1367545, 4324555, 13675445, 43245553, 136754447, 432455532, 1367544468, 4324555320, 13675444680, 43245553203, 136754446797, 432455532033, 1367544467967
(list; graph; listen)
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OFFSET
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0,1
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EXAMPLE
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a(4)=43 because there are 43 heptagonal numbers with 4 digits.
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MAPLE
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Digits := 20: A117718 := proc(n) if n = 1 then 3; else ceil(3/10*(1+sqrt(1+40*10^n/9))-1) - ceil(3/10*(1+sqrt(40*10^(n-1)/9))) +1 ; fi ; end: seq(A117718(n), n=1..30) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 22 2008
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CROSSREFS
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Cf. A000566.
Sequence in context: A057433 A006074 A081714 this_sequence A086826 A130409 A071167
Adjacent sequences: A117715 A117716 A117717 this_sequence A117719 A117720 A117721
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KEYWORD
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base,nonn
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AUTHOR
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Luc Stevens (lms022(AT)yahoo.com), Apr 13 2006
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 22 2008
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