a(n) = floor(sqrt(a(n-1)^2 + a(n-2)^2 + a(n-1)*a(n-2))), a(1)=1, a(2)=3.

Terms

a(0) =1a(1) =3a(2) =3a(3) =5a(4) =7a(5) =10a(6) =14a(7) =20a(8) =29a(9) =42a(10) =61a(11) =89a(12) =130a(13) =190a(14) =278a(15) =407a(16) =596a(17) =873a(18) =1279a(19) =1874a(20) =2746a(21) =4024a(22) =5897a(23) =8642a(24) =12665a(25) =18561a(26) =27202a(27) =39866a(28) =58426a(29) =85627