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

0,2

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

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

Prog

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

Crossrefs

Cf. A061601.

Sequence in context: A179186 A349081 A192045 * A138666 A072835 A367035

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

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

Status

approved