This site is supported by donations to The OEIS Foundation.

Annual Appeal: Please make a donation (tax deductible in USA) to keep the OEIS running. Over 5000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A084021 Product of n and its 9's complement. 2
 8, 14, 18, 20, 20, 18, 14, 8, 0, 890, 968, 1044, 1118, 1190, 1260, 1328, 1394, 1458, 1520, 1580, 1638, 1694, 1748, 1800, 1850, 1898, 1944, 1988, 2030, 2070, 2108, 2144, 2178, 2210, 2240, 2268, 2294, 2318, 2340, 2360, 2378, 2394, 2408, 2420, 2430, 2438 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS There are infinitely many nonzero squares in this sequence; for example a(10^(4n)-10^(2n)) = [10^n*(10^(2n)-1)]^2. - David Wasserman, Dec 07 2004 LINKS FORMULA a(n) = n*(10^d -1-n), where d is the number of digits in n. a(n) = n*A061601(n). - David Wasserman, Dec 07 2004 CROSSREFS Cf. A061601. Sequence in context: A235143 A179186 A192045 * A138666 A072835 A096229 Adjacent sequences:  A084018 A084019 A084020 * A084022 A084023 A084024 KEYWORD base,easy,nonn AUTHOR Amarnath Murthy, May 23 2003 EXTENSIONS More terms from David Wasserman, Dec 07 2004 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.