A084021 Product of n and its 9's complement.

0, 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

Offset: 0

Author

Amarnath Murthy, May 23 2003

Keywords

• base
• easy
• nonn

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

• Seiichi Manyama, Table of n, a(n) for n = 0..9999

Crossrefs

Cf. A061601.

Programs

PARI

{a(n) = n*(10^length(Str(n))-1-n)} \\ Seiichi Manyama, Sep 15 2019

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

Extensions

More terms from David Wasserman, Dec 07 2004

a(0)=0 prepended by Seiichi Manyama, Sep 15 2019