Sum of numbers in the n-th antidiagonal of the reciprocity array of 3.

Terms

a(0) =3a(1) =6a(2) =13a(3) =19a(4) =34a(5) =55a(6) =84a(7) =120a(8) =174a(9) =231a(10) =310a(11) =399a(12) =510a(13) =634a(14) =786a(15) =948a(16) =1144a(17) =1359a(18) =1602a(19) =1863a(20) =2176a(21) =2496a(22) =2860a(23) =3256a(24) =3680a(25) =4147a(26) =4662a(27) =5189a(28) =5782a(29) =6412