A028400 a(n) = (2^n + 1)^2.

4, 9, 25, 81, 289, 1089, 4225, 16641, 66049, 263169, 1050625, 4198401, 16785409, 67125249, 268468225, 1073807361, 4295098369, 17180131329, 68720001025, 274878955521, 1099513724929, 4398050705409, 17592194433025

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• easy

Links

• H. Bottomley, Illustration of initial terms
• I. Strazdins, Universal affine classification of Boolean functions, Acta Applic. Math. 46 (1997), 147-167.
• Index entries for linear recurrences with constant coefficients, signature (7,-14,8).

Programs

Mathematica

LinearRecurrence[{7,-14,8},{4,9,25},30] (* Harvey P. Dale, Aug 02 2025 *)

PARI

a(n)=(2^n + 1)^2

Formula

a(n) = A000051(n)^2. - R. J. Mathar, Nov 27 2015

G.f.: ( -4+19*x-18*x^2 ) / ( (x-1)*(2*x-1)*(4*x-1) ). - R. J. Mathar, Nov 27 2015