Central trinomial coefficients: largest coefficient of (1 + x + x^2)^n.

Terms

a(0) =1a(1) =1a(2) =3a(3) =7a(4) =19a(5) =51a(6) =141a(7) =393a(8) =1107a(9) =3139a(10) =8953a(11) =25653a(12) =73789a(13) =212941a(14) =616227a(15) =1787607a(16) =5196627a(17) =15134931a(18) =44152809a(19) =128996853a(20) =377379369a(21) =1105350729a(22) =3241135527a(23) =9513228123a(24) =27948336381a(25) =82176836301a(26) =241813226151a(27) =712070156203