A087288 a(n)=2a(n-1)+a(n-2)-2a(n-3).

4, 4, 10, 16, 34, 64, 130, 256, 514, 1024, 2050, 4096, 8194, 16384, 32770, 65536, 131074, 262144, 524290, 1048576, 2097154, 4194304, 8388610, 16777216, 33554434, 67108864, 134217730, 268435456, 536870914, 1073741824, 2147483650

Offset: 0

Author

Mario Catalani (mario.catalani(AT)unito.it), Aug 31 2003

Keywords

• nonn
• easy

Comments

a(n)=(A000051(n)-A014551(n))/2.

Links

• Indranil Ghosh, Table of n, a(n) for n = 0..3314
• Index entries for linear recurrences with constant coefficients, signature (2,1,-2).

Programs

Mathematica

CoefficientList[Series[(4 - 4x - 2x^2)/(1 - 2x - x^2 + 2x^3), {x, 0, 30}], x]

PARI

a(n)=2<Charles R Greathouse IV, Aug 20 2013

Formula

G.f.: (4-4x-2x^2)/(1-2x-x^2+2x^3). a(n)=2^(n+1)+1+(-1)^n.