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A117712
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Number of pentagonal numbers with n digits.
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1
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3, 6, 17, 56, 177, 558, 1766, 5583, 17655, 55829, 176550, 558297, 1765493, 5582976, 17654924, 55829769, 176549231, 558297692, 1765492316, 5582976912, 17654923165, 55829769118, 176549231655, 558297691180, 1765492316544, 5582976911806, 17654923165439
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,1
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LINKS
| Harvey P. Dale, Table of n, a(n) for n = 0..1000
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EXAMPLE
| a(4)= 56 because there are 56 pentagonal numbers with 4 digits.
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MATHEMATICA
| nm[n_] := Floor[(1 + Sqrt[1 + 24 n])/6]; Join[{3}, Differences[ Table[nm[10^i], {i, 30}]]] (* From Harvey P. Dale, Oct 19 2011 *)
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CROSSREFS
| Cf. A000326.
Sequence in context: A099511 A204517 A143093 * A106158 A003323 A073591
Adjacent sequences: A117709 A117710 A117711 * A117713 A117714 A117715
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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 Harvey P. Dale, Oct 19 2011
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