Template:Sequence of the Day for March 21

Intended for: March 21, 2013

Timetable

• First draft entered by Alonso del Arte on June 10, 2012 ✓
• Draft reviewed by Daniel Forgues on March 21, 2013 ✓
• Draft to be approved by February 21, 2013

Yesterday's SOTD * Tomorrow's SOTD

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A116700: “Early bird” numbers. (In base 10.)

{ 12, 21, 23, 31, 32, 34, 41, 42, 43, ... }

Concatenate the [base 10 representation of] natural numbers into the string 12345678910111213.... The sequence gives the numbers which occur in the string ahead of their “natural” place. For example, 12 appears at position 14 (the first nine positions are for the numbers 1 to 9, then 10 at position 10 and 11 at position 12), but it also appears at position 1.

The complement of A116700 gives what might be called "punctual bird" numbers (A131881). (Obviously, there can't be “late bird” numbers!)