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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A266094 a(n) is the sum of the divisors of the smallest number k such that the symmetric representation of sigma(k) has n parts. 2
1, 4, 13, 32, 104, 228, 576, 1408, 4104, 9824, 19152, 39816, 82944, 196992, 441294, 881280, 1911168, 4539024 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For more information see A239663 and A239665.

LINKS

Table of n, a(n) for n=1..18.

FORMULA

a(n) = A000203(A239663(n)).

EXAMPLE

Illustration of the symmetric representation of sigma(9):

.

.     _ _ _ _ _ 5

.    |_ _ _ _ _|

.              |_ _ 3

.              |_  |

.                |_|_ _ 5

.                    | |

.                    | |

.                    | |

.                    | |

.                    |_|

.

For n = 3 we have that 9 is the smallest number whose symmetric representation of sigma has three parts: [5, 3, 5], so a(3) = 5 + 3 + 5 = 13, equaling the sum of divisors of 9: sigma(9) = 1 + 3 + 9 = 13.

For n = 7 we have that 357 is the smallest number whose symmetric representation of sigma has seven parts: [179, 61, 29, 38, 29, 61, 179], so a(7) = 179 + 61 + 29 + 38 + 29 + 61 + 179 = 576, equaling the sum of divisors of 357: sigma(357) = 1 + 3 + 7 + 17 + 21 + 51 + 119 + 357 = 576.

CROSSREFS

Cf. A000203, A196020, A235791, A236104, A237048, A237270, A237271, A237591, A237593, A239931-A239934, A239663, A239665, A240062, A245092, A262626.

Sequence in context: A208638 A173277 A036420 * A054039 A302082 A124669

Adjacent sequences:  A266091 A266092 A266093 * A266095 A266096 A266097

KEYWORD

nonn,hard,more

AUTHOR

Omar E. Pol, Dec 21 2015

EXTENSIONS

a(14)-a(18) from Omar E. Pol, Jul 21 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 February 22 09:43 EST 2019. Contains 320390 sequences. (Running on oeis4.)