a(n) = 49*(n*(n+1)/2) + 6.

Terms

a(0) =6a(1) =55a(2) =153a(3) =300a(4) =496a(5) =741a(6) =1035a(7) =1378a(8) =1770a(9) =2211a(10) =2701a(11) =3240a(12) =3828a(13) =4465a(14) =5151a(15) =5886a(16) =6670a(17) =7503a(18) =8385a(19) =9316a(20) =10296a(21) =11325a(22) =12403a(23) =13530a(24) =14706a(25) =15931a(26) =17205a(27) =18528a(28) =19900a(29) =21321