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 A317305 Sum of divisors of the numbers whose divisors increase by a factor of 2 or less. 3
 1, 3, 7, 12, 15, 28, 31, 39, 42, 60, 56, 72, 63, 91, 90, 96, 124, 120, 120, 168, 127, 144, 195, 186, 224, 180, 234, 252, 217, 210, 280, 248, 360, 312, 255, 336, 336, 403, 372, 292, 378, 363, 480, 372, 546, 508, 399, 468, 465, 504, 434, 576, 600, 504, 504, 560, 546, 744, 728, 511 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also sum of divisors of the numbers k whose symmetric representation of sigma(k) has only one part. For more information see A237593 and its related sequences. LINKS FORMULA a(n) = A000203(A174973(n)) = A000203(A238443(n)). EXAMPLE Illustration of initial terms. a(n) is the area (or the numbers of cells) of the n-th region of the diagram: .          _ _   _   _   _       _       _   _   _       _       _   _   _ .    1    |_| | | | | | | |     | |     | | | | | |     | |     | | | | | | .    3    |_ _|_| | | | | |     | |     | | | | | |     | |     | | | | | | .          _ _|  _|_| | | |     | |     | | | | | |     | |     | | | | | | .    7    |_ _ _|    _|_| |     | |     | | | | | |     | |     | | | | | | .          _ _ _|  _|  _ _|     | |     | | | | | |     | |     | | | | | | .   12    |_ _ _ _|  _|    _ _ _| |     | | | | | |     | |     | | | | | | .          _ _ _ _| |    _|    _ _|     | | | | | |     | |     | | | | | | .   15    |_ _ _ _ _|  _|     |    _ _ _| | | | | |     | |     | | | | | | .                     |      _|   |  _ _ _|_| | | |     | |     | | | | | | .                     |  _ _|    _| |    _ _ _|_| |     | |     | | | | | | .          _ _ _ _ _ _| |      _|  _|   |  _ _ _ _|     | |     | | | | | | .   28    |_ _ _ _ _ _ _|  _ _|  _|  _ _| |    _ _ _ _ _| |     | | | | | | .                         |  _ _|  _|    _|   |    _ _ _ _|     | | | | | | .                         | |     |     |  _ _|   |    _ _ _ _ _| | | | | | .          _ _ _ _ _ _ _ _| |  _ _|  _ _|_|       |   |  _ _ _ _ _|_| | | | .   31    |_ _ _ _ _ _ _ _ _| |  _ _|  _|      _ _|   | |    _ _ _ _ _|_| | .          _ _ _ _ _ _ _ _ _| | |     |      _|    _ _| |   |  _ _ _ _ _ _| .   39    |_ _ _ _ _ _ _ _ _ _| |  _ _|    _|  _ _|  _ _|   | | .          _ _ _ _ _ _ _ _ _ _| | |       |   |    _|    _ _| | .   42    |_ _ _ _ _ _ _ _ _ _ _| |  _ _ _|  _|  _|     |  _ _| .                                 | |       |  _|      _| | .                                 | |  _ _ _| |      _|  _| .          _ _ _ _ _ _ _ _ _ _ _ _| | |  _ _ _|  _ _|  _| .   60    |_ _ _ _ _ _ _ _ _ _ _ _ _| | |       |  _ _| .                                     | |  _ _ _| | .                                     | | |  _ _ _| .          _ _ _ _ _ _ _ _ _ _ _ _ _ _| | | | .   56    |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _| | | .          _ _ _ _ _ _ _ _ _ _ _ _ _ _ _| | | .   72    |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _| | .          _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _| | .   63    |_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _| . The diagram shows the first 13 terms of the sequence. The symmetric representation of sigma of the numbers A174973: 1, 2, 4, 6, 8, 12, 16, 18, 20, 24, 28, 30, 32, ..., has only one part. The length of the largest Dyck path of the n-th region of the diagram equals A047836(n). The semilength equals A174973(n). CROSSREFS Cf. A317307 is a subsequence. Cf. A000203, A047836, A174973, A196020, A236104, A235791, A237048, A237591, A237593, A237270, A237271, A238443, A239660, A239931, A239932, A239933, A239934, A244050, A245092, A262626. Sequence in context: A075895 A033015 A225574 * A096998 A317307 A122981 Adjacent sequences:  A317302 A317303 A317304 * A317306 A317307 A317308 KEYWORD nonn AUTHOR Omar E. Pol, Aug 25 2018 STATUS approved

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Last modified December 8 12:31 EST 2019. Contains 329864 sequences. (Running on oeis4.)