a(n) = floor(exp(Pi*sqrt(n))).

Terms

a(0) =1a(1) =23a(2) =85a(3) =230a(4) =535a(5) =1124a(6) =2197a(7) =4071a(8) =7228a(9) =12391a(10) =20631a(11) =33506a(12) =53252a(13) =83047a(14) =127358a(15) =192400a(16) =286751a(17) =422150a(18) =614551a(19) =885479a(20) =1263794a(21) =1787960a(22) =2508951a(23) =3493969a(24) =4831163a(25) =6635623a(26) =9056943a(27) =12288743a(28) =16580630a(29) =22253151