4-dimensional centered tetrahedral numbers.

Terms

a(0) =1a(1) =6a(2) =21a(3) =56a(4) =126a(5) =251a(6) =456a(7) =771a(8) =1231a(9) =1876a(10) =2751a(11) =3906a(12) =5396a(13) =7281a(14) =9626a(15) =12501a(16) =15981a(17) =20146a(18) =25081a(19) =30876a(20) =37626a(21) =45431a(22) =54396a(23) =64631a(24) =76251a(25) =89376a(26) =104131a(27) =120646a(28) =139056a(29) =159501