A201123 Differences between odd powers of 7 and the next smaller square.

3, 19, 166, 894, 5703, 12654, 620046, 4235622, 24518766, 133763479, 575536407, 7275224659, 63521178243, 36407018199, 1783943891751, 12048048160062, 62797942092807, 615169213046419, 4293026969512678, 29406470217788179, 174254081653289398, 2627356192258967382

Offset: 1

Author

Hugo Pfoertner, Nov 27 2011

Keywords

• nonn

Examples

			a(1) = 7^1 - 2^2 = 3;
a(2) = 7^3 - 18^2 = 343 - 324 = 19;
a(3) = 7^5 - 129^2 = 16807 - 16641 = 166.
		

Links

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

Crossrefs

Cf. A051218.

Programs

Mathematica

Table[7^(2 n - 1) - Floor[Sqrt[7^(2 n - 1)]]^2, {n, 30}] (* Wesley Ivan Hurt, Mar 06 2014 *)

Formula

a(n) = 7^(2*n-1) - floor(sqrt(7^(2*n-1)))^2.