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A128826 a(n) = 10^(2n-1) minus largest square less than 10^(2n-1). 2
1, 39, 144, 1756, 49116, 484471, 4175271, 38053824, 10649244, 1064924400, 43246886799, 529955487744, 2399106211776, 50173961567511, 590207432515431, 2099745368512359, 20237877241133151, 126421128012287511 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

For even indices a(2k) = 2*10^k-1, hence only odd powers of 10 are considered in this sequence.

LINKS

Hugo Pfoertner, Table of n, a(n) for n = 1..500

FORMULA

a(n)=10^(2n-1)-A061433(2n-1).

a(n) = 10^(2*n-1) - floor(sqrt(10^(2*n-1)))^2.

EXAMPLE

a(1) = 1 because 10 - 3^2 = 1.

a(2) = 39 because 1000 - 31^2 = 39.

a(3) = 144 because 100000 - 316^2 = 144.

MATHEMATICA

Table[10^n-Floor[(10^n-1)^(1/2)]^2, {n, 1, 40, 2}]

CROSSREFS

Cf. A061433, A051221.

Sequence in context: A044371 A044752 A072253 * A240902 A158593 A158598

Adjacent sequences:  A128823 A128824 A128825 * A128827 A128828 A128829

KEYWORD

nonn

AUTHOR

Zak Seidov, Apr 12 2007

STATUS

approved

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Last modified July 31 13:25 EDT 2021. Contains 346373 sequences. (Running on oeis4.)