a(0) = a(1) = a(2) = 1, a(n) = largest prime <= a(n-1) + a(n-2) + a(n-3).

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =5a(5) =7a(6) =13a(7) =23a(8) =43a(9) =79a(10) =139a(11) =257a(12) =467a(13) =863a(14) =1583a(15) =2909a(16) =5351a(17) =9839a(18) =18097a(19) =33287a(20) =61223a(21) =112603a(22) =207113a(23) =380929a(24) =700643a(25) =1288657a(26) =2370223a(27) =4359517a(28) =8018383a(29) =14748119