a(n) = [x^n] Product_{k=1..n} (x^(k*(k+1)/2) + 1 + 1/x^(k*(k+1)/2)).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =5a(6) =11a(7) =25a(8) =56a(9) =129a(10) =313a(11) =748a(12) =1831a(13) =4584a(14) =11581a(15) =29555a(16) =76398a(17) =199191a(18) =522746a(19) =1382158a(20) =3676072a(21) =9828631a(22) =26412174a(23) =71310248a(24) =193346941a(25) =526302232a(26) =1437895915a(27) =3941671019a(28) =10839118898a(29) =29893768219