a(n)=T(n,n+1), array T as in A049735.

Terms

a(0) =5a(1) =21a(2) =45a(3) =81a(4) =137a(5) =193a(6) =277a(7) =357a(8) =457a(9) =577a(10) =697a(11) =845a(12) =981a(13) =1153a(14) =1321a(15) =1505a(16) =1725a(17) =1933a(18) =2161a(19) =2393a(20) =2629a(21) =2917a(22) =3181a(23) =3489a(24) =3769a(25) =4093a(26) =4421a(27) =4741a(28) =5129a(29) =5465