A154890 Jacobsthal numbers A001045 alternatingly incremented by 3 and 5.

3, 6, 4, 8, 8, 16, 24, 48, 88, 176, 344, 688, 1368, 2736, 5464, 10928, 21848, 43696, 87384, 174768, 349528, 699056, 1398104, 2796208, 5592408, 11184816, 22369624, 44739248, 89478488, 178956976, 357913944, 715827888, 1431655768, 2863311536, 5726623064

Offset: 0

Author

Paul Curtz, Jan 17 2009

Keywords

• nonn
• easy

Formula

a(2n+1) = 2*a(2n).

a(n) = A153643(n)+A010684(n).

a(n+2) = 4*A128209(n).

a(n) = 2*a(n-1)+a(n-2)-2*a(n-3). G.f.: (3-11x^2)/((1-x)(1+x)(1-2x)). [R. J. Mathar, Jan 23 2009]

Extensions

Edited and extended by R. J. Mathar, Jan 23 2009