A145544 a(n) = 4*(4^n-3^n).

0, 4, 28, 148, 700, 3124, 13468, 56788, 235900, 969844, 3958108, 16068628, 64983100, 262058164, 1054609948, 4237571668, 17007682300, 68202916084, 273328224988, 1094862581908, 4384099373500, 17550344631604, 70243219939228, 281098403995348, 1124770188696700

Offset

0,2

Comments

Suggested by a discussion on the Sequence Fans Mailing List; the formula is due to Jaume Oliver Lafont.

Links

Table of n, a(n) for n=0..24.

Index entries for linear recurrences with constant coefficients, signature (7,-12)

Formula

a(n) = 4*A005061(n) = 7*a(n-1)-12*a(n-2). G.f.: 4*x/((4*x-1)*(3*x-1)). [R. J. Mathar, Mar 18 2009]

a(n) = A005061(n)*4. [Omar E. Pol, Mar 18 2009]

Crossrefs

Cf. A005061.

Sequence in context: A320397 A273611 A043013 * A006302 A272992 A272747

Adjacent sequences: A145541 A145542 A145543 * A145545 A145546 A145547

Keyword

nonn,easy

Author

N. J. A. Sloane, Mar 18 2009

Status

approved