Number of compositions of 5*n into parts 1 and 5.

Terms

a(0) =1a(1) =2a(2) =8a(3) =34a(4) =140a(5) =571a(6) =2328a(7) =9496a(8) =38740a(9) =158045a(10) =644761a(11) =2630364a(12) =10730820a(13) =43777405a(14) =178594110a(15) =728591751a(16) =2972359720a(17) =12126025705a(18) =49469281395a(19) =201814663875a(20) =823322219501