This site is supported by donations to The OEIS Foundation.

Template:Sequence of the Day for March 25

From OeisWiki
Jump to: navigation, search


Intended for: March 25, 2013

Timetable

  • First draft entered by Alonso del Arte on January 12, 2012
  • Draft reviewed by Daniel Forgues on March 14, 2016
  • Draft to be approved by February 25, 2013

Yesterday's SOTD * Tomorrow's SOTD

The line below marks the end of the <noinclude> ... </noinclude> section.



A018834: Numbers
n
such that decimal expansion of
n 2
contains
n
as a substring.
{ 5, 6, 10, 25, 50, 60, 76, 100, ... }

Most of the terms of this sequence are rather predictable. All the powers of 10 should be in the sequence. Review of the squares of the numbers 1 to 9 suggests that there should be at least a few terms ending in 5 or 6. So it is a pleasant surprise to find 3792 as a term: its square is 14379264. The substring doesn't have to be at the end, as with multiples of 5 or 6, nor at the beginning, as with the powers of 10.