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A117718 Number of heptagonal numbers with n digits. 1
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; text; internal format)
OFFSET
0,1
LINKS
EXAMPLE
a(4)=43 because there are 43 heptagonal numbers with 4 digits.
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, Jan 22 2008
CROSSREFS
Cf. A000566.
Sequence in context: A057433 A006074 A081714 * A268700 A349001 A176857
KEYWORD
base,nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 13 2006
EXTENSIONS
More terms from R. J. Mathar, Jan 22 2008
STATUS
approved

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Last modified May 26 16:43 EDT 2024. Contains 372840 sequences. (Running on oeis4.)