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

Author

Hugo Pfoertner, Nov 27 2011

Keywords

• nonn

Examples

			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
		

Links

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

Crossrefs

Cf. A051214

Programs

Mathematica

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

Formula

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