A068824 a(n) = n*c(n), where c(n) is the 10's complement of n.

9, 16, 21, 24, 25, 24, 21, 16, 9, 900, 979, 1056, 1131, 1204, 1275, 1344, 1411, 1476, 1539, 1600, 1659, 1716, 1771, 1824, 1875, 1924, 1971, 2016, 2059, 2100, 2139, 2176, 2211, 2244, 2275, 2304, 2331, 2356, 2379

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Formula

G.f.: -2*x^2/(1-x)^3 + (9/(1-x)^2)*Sum_{k=0..infinity} (10^(2*d)*x^(10^d)-(10^(2*d)-10^d)*x^(1+10^d)). - Robert Israel, Aug 18 2019

Example

a(45) = 2475 as 10's complement of 45 is 100-45 = 55 and 45*55 = 2475.

Maple

seq((10^(1+ilog10(n))-n)*n, n=1..100); # Robert Israel, Aug 18 2019

Mathematica

#*(10^(IntegerLength[#]) - #) & /@ Range[39] (* Jayanta Basu, Aug 07 2013 *)

Crossrefs

Sequence in context: A048279 A250656 A072836 * A095961 A356295 A045911

Adjacent sequences: A068821 A068822 A068823 * A068825 A068826 A068827

Keyword

easy,nonn,base

Author

Amarnath Murthy, Mar 08 2002

Status

approved