Balancing weights on the integer line.

Terms

a(0) =1a(1) =2a(2) =5a(3) =12a(4) =32a(5) =94a(6) =289a(7) =910a(8) =2934a(9) =9686a(10) =32540a(11) =110780a(12) =381676a(13) =1328980a(14) =4669367a(15) =16535154a(16) =58965214a(17) =211591218a(18) =763535450a(19) =2769176514a(20) =10089240974a(21) =36912710568a(22) =135565151486a(23) =499619269774