|
Search: id:A101639
|
|
|
| A101639 |
|
Positive integers n for which n = f(n), where f(n) is the total number of 2's required when writing out all numbers between 0 and n. |
|
+0
10
|
|
| 28263827, 35000000, 242463827, 500000000, 528263827, 535000000, 10000000000, 10028263827, 10035000000, 10242463827, 10500000000, 10528263827, 10535000000
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Related to a problem posed by Google and discussed on the MathWorld link.
This is the complete list of all 13 positive numbers n such that n is equal to the number of 2's in the decimal digits of all numbers <= n. - Daniel Hirschberg (dan(AT)ics.uci.edu), May 05 2007
|
|
LINKS
|
Mathworld, A problem posed by Google
|
|
EXAMPLE
|
a(1) = 28263827 since writing out all numbers from 0 to 28263827 requires that 28263827 2's be used and since 28263827 is the first such positive integer.
a(4)=500000000 because the number of 2's in the decimal digits of the numbers from 1 to 500000000 is 500000000, and this is the 4th such number.
|
|
CROSSREFS
|
Cf. A014778 for proof these sequences are finite; Also A101640, A101641, A130427, A130428, A130429, A130430, A130431; cf. A130432 for the number of numbers in these sequences.
Sequence in context: A069342 A018187 A114681 this_sequence A112640 A104828 A105013
Adjacent sequences: A101636 A101637 A101638 this_sequence A101640 A101641 A101642
|
|
KEYWORD
|
base,fini,nonn,full
|
|
AUTHOR
|
Ryan Propper (rpropper(AT)stanford.edu), Dec 10 2004
|
|
EXTENSIONS
|
More terms from Daniel Hirschberg (dan(AT)ics.uci.edu), May 05 2007
|
|
|
Search completed in 0.002 seconds
|
