A132133 Number of n-digit "Punctual Birds" (cf. A131881).

1, 9, 45, 270, 2104, 16941, 142245, 1226146

Offset: 0

Author

Graeme McRae, Aug 11 2007

Keywords

• base
• nonn
• more

Comments

The number of n-digit "Early Birds" is 9*10^(n-1) - A132133(n), which is 0, 45, 630, 6896, 73059, 757755, 7773854, ... for n = 1, 2, ...

Here a(0) = 1 corresponds to the number 0 which is punctual in the sense that it does not occur before position 0, and which may be considered to have 0 digits for convenience: The index of 10^n in A131881 is then Sum_{k=0..n} a(k). - M. F. Hasler, Oct 25 2019

Examples

			a(2) = 45 because there are 45 2-digit Punctual Birds (10, 11, 13-20, 22, 24-30, 33, 35-40, 44, 46-50, 55, 57-60, 66, 68-70, 77, 79, 80, 88 and 90)
		

Crossrefs

Cf. A033307, A117804, A116700, A131881, A132131, A132132.

Extensions

Extended to a(0) = 1 by M. F. Hasler, Oct 25 2019