login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A347980 a(n) is the smallest odd number k whose symmetric representation of sigma(k) has maximum width n. 5
1, 15, 315, 2145, 3465, 17325, 45045, 51975, 225225, 405405, 315315, 765765, 1576575, 2297295 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The sequence is not increasing with the maximum width of the symmetric representation just like A347979.

Observation: a(2)..a(14) ending in 5. - Omar E. Pol, Sep 23 2021

LINKS

Table of n, a(n) for n=1..14.

EXAMPLE

The pattern of maximum widths of the parts in the symmetric representation of sigma for the first four terms in the sequence is:

   a(n) parts  successive widths

     1:   1          1

    15:   3        1 2 1

   315:   3        1 3 1

  2145:   7    1 2 3 4 3 2 1

MATHEMATICA

a262045[n_] := Module[{a=Accumulate[Map[If[Mod[n - # (#+1)/2, #]==0, (-1)^(#+1), 0] &, Range[Floor[(Sqrt[8n+1]-1)/2]]]]}, Join[a, Reverse[a]]]

a347980[n_, mw_] := Module[{list=Table[0, mw], i, v}, For[i=1, i<=n, i+=2, v=Max[a262045[i]]; If [list[[v]]==0, list[[v]]=i]]; list]

a347980[2500000, 14] (* long evaluation time *)

CROSSREFS

Cf. A174973, A237048, A237270, A237271, A237591, A237593, A238443, A249351 (widths), A250070, A262045, A341969, A341970, A341971, A347979.

Sequence in context: A158533 A284070 A133766 * A289951 A112489 A062757

Adjacent sequences:  A347977 A347978 A347979 * A347981 A347982 A347983

KEYWORD

nonn,more

AUTHOR

Hartmut F. W. Hoft, Sep 22 2021

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 2 05:01 EST 2021. Contains 349437 sequences. (Running on oeis4.)