A084861 Expansion of (1-3x+4x^2-3x^3+x^4)/(1-2x)^2.

1, 1, 4, 9, 21, 48, 108, 240, 528, 1152, 2496, 5376, 11520, 24576, 52224, 110592, 233472, 491520, 1032192, 2162688, 4521984, 9437184, 19660800, 40894464, 84934656, 176160768, 364904448, 754974720, 1560281088, 3221225472

Offset: 0

Author

Paul Barry, Jun 12 2003

Keywords

• easy
• nonn

Comments

Partial sums give A084860. Binomial transform of signed version of A008795.

Links

• Index entries for linear recurrences with constant coefficients, signature (4,-4).

Programs

Mathematica

CoefficientList[Series[(1-3x+4x^2-3x^3+x^4)/(1-2x)^2,{x,0,40}],x] (* or *) LinearRecurrence[{4,-4},{1,1,4,9,21},40] (* Harvey P. Dale, Nov 25 2020 *)

Formula

a(n) = 3(n+3)2^(n-4), n>2.