A201124 Differences between odd powers of 3 and the next smaller square

2, 2, 18, 71, 83, 747, 1679, 7538, 22394, 65186, 177578, 370898, 1497119, 2428283, 5285858, 47572722, 129918074, 274553378, 1128916463, 2107864523, 6892205234, 25794120683, 14732727599, 132594548391, 214986322034, 1934876898306, 8608610563379, 24645805942151, 63317186094563, 94369472696663

Offset

1,1

Links

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

Formula

a(n) = 3^(2*n-1) - floor(sqrt(3^(2*n-1)))^2

Example

a(1)=3^1-1^2=2, a(2)=3^3-5^2=27-25=2, a(3)=3^5-15^2=243-225=18

Mathematica

 #-Floor[Sqrt[#]]^2&/@(3^Range[1, 61, 2])  (* Harvey P. Dale, Nov 01 2022 *)

Crossrefs

Cf. A051214

Sequence in context: A136434 A121670 A001183 * A173785 A264715 A294341

Adjacent sequences: A201121 A201122 A201123 * A201125 A201126 A201127

Keyword

nonn

Author

Hugo Pfoertner, Nov 27 2011

Status

approved