The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 Table of n, a(n) for n=0..24. 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 Adjacent sequences: A117715 A117716 A117717 * A117719 A117720 A117721 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

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