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A117718
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Number of heptagonal numbers with n digits.
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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; refs; listen; history; internal format)
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OFFSET
| 0,1
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EXAMPLE
| a(4)=43 because there are 43 heptagonal numbers with 4 digits.
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MAPLE
| 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
| Cf. A000566.
Sequence in context: A057433 A006074 A081714 * A176857 A086826 A130409
Adjacent sequences: A117715 A117716 A117717 * A117719 A117720 A117721
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KEYWORD
| base,nonn
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AUTHOR
| Luc Stevens (lms022(AT)yahoo.com), Apr 13 2006
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 22 2008
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