Centered 9-gonal (also known as nonagonal or enneagonal) numbers. Every third triangular number, starting with a(1)=1.

A060544

Centered 9-gonal (also known as nonagonal or enneagonal) numbers. Every third triangular number, starting with a(1)=1.

Terms

    a(0) =1a(1) =10a(2) =28a(3) =55a(4) =91a(5) =136a(6) =190a(7) =253a(8) =325a(9) =406a(10) =496a(11) =595a(12) =703a(13) =820a(14) =946a(15) =1081a(16) =1225a(17) =1378a(18) =1540a(19) =1711a(20) =1891a(21) =2080a(22) =2278a(23) =2485a(24) =2701a(25) =2926a(26) =3160a(27) =3403a(28) =3655a(29) =3916

External references