login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Table of n, a(n) for n=1..60.

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

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

License Agreements, Terms of Use, Privacy Policy. .

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