Coefficient of x^n in the expansion of ( (1+x) / (1-x^3) )^n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =4a(4) =17a(5) =51a(6) =142a(7) =442a(8) =1457a(9) =4702a(10) =14951a(11) =48038a(12) =156158a(13) =508860a(14) =1658112a(15) =5414754a(16) =17735473a(17) =58209803a(18) =191310964a(19) =629605300a(20) =2074916167a(21) =6846553375a(22) =22615507300a(23) =74775856026a(24) =247463508542a(25) =819645776926