A261056 Expansion of ( 2-x^2 ) / (x^2+2*x-1)^2 .

2, 8, 27, 84, 248, 708, 1973, 5400, 14574, 38896, 102863, 269964, 703972, 1825612, 4711785, 12110064, 31010266, 79148184, 201420163, 511233156, 1294489296, 3270662036, 8247316765, 20758752648, 52163239622, 130875524096, 327893289783, 820410399804, 2050189683644

Offset: 0

Author

R. J. Mathar, Aug 08 2015

Keywords

• nonn
• easy

Comments

2nd column of A210637.

Links

• Index entries for linear recurrences with constant coefficients, signature (4,-2,-4,-1)

Crossrefs

Cf. A210637.

Programs

Mathematica

CoefficientList[Series[(2-x^2)/(x^2+2*x-1)^2,{x,0,40}],x] (* or *) LinearRecurrence[{4,-2,-4,-1},{2,8,27,84},40] (* Harvey P. Dale, Feb 24 2017 *)

Formula

a(n) = 2*A006645(n+2) -A006645(n).