a(n) = 5*n*(n+1)/2 - 4.

Terms

a(0) =1a(1) =11a(2) =26a(3) =46a(4) =71a(5) =101a(6) =136a(7) =176a(8) =221a(9) =271a(10) =326a(11) =386a(12) =451a(13) =521a(14) =596a(15) =676a(16) =761a(17) =851a(18) =946a(19) =1046a(20) =1151a(21) =1261a(22) =1376a(23) =1496a(24) =1621a(25) =1751a(26) =1886a(27) =2026a(28) =2171a(29) =2321