Triangular numbers plus quarter-squares: n*(n+1)/2 + floor((n+1)^2/4) (i.e., A000217(n) + A002620(n+1)).

A001859

Triangular numbers plus quarter-squares: n*(n+1)/2 + floor((n+1)^2/4) (i.e., A000217(n) + A002620(n+1)).

Terms

    a(0) =0a(1) =2a(2) =5a(3) =10a(4) =16a(5) =24a(6) =33a(7) =44a(8) =56a(9) =70a(10) =85a(11) =102a(12) =120a(13) =140a(14) =161a(15) =184a(16) =208a(17) =234a(18) =261a(19) =290a(20) =320a(21) =352a(22) =385a(23) =420a(24) =456a(25) =494a(26) =533a(27) =574a(28) =616a(29) =660

External references