A lower diagonal of pendular trinomial triangle A119369.

Terms

a(0) =1a(1) =2a(2) =6a(3) =20a(4) =70a(5) =253a(6) =938a(7) =3546a(8) =13617a(9) =52967a(10) =208255a(11) =826315a(12) =3304456a(13) =13304924a(14) =53891402a(15) =219442686a(16) =897772983a(17) =3688451380a(18) =15211545938a(19) =62950542636a(20) =261329456566