Second heptagonal numbers: a(n) = n*(5*n+3)/2.

Terms

a(0) =0a(1) =4a(2) =13a(3) =27a(4) =46a(5) =70a(6) =99a(7) =133a(8) =172a(9) =216a(10) =265a(11) =319a(12) =378a(13) =442a(14) =511a(15) =585a(16) =664a(17) =748a(18) =837a(19) =931a(20) =1030a(21) =1134a(22) =1243a(23) =1357a(24) =1476a(25) =1600a(26) =1729a(27) =1863a(28) =2002a(29) =2146