[ (2nd elementary symmetric function of 3,4,...,n+3)/(3+4+...+n+3) ].

Terms

a(0) =1a(1) =3a(2) =6a(3) =9a(4) =13a(5) =17a(6) =22a(7) =27a(8) =33a(9) =39a(10) =46a(11) =53a(12) =60a(13) =69a(14) =77a(15) =86a(16) =96a(17) =106a(18) =117a(19) =128a(20) =140a(21) =152a(22) =165a(23) =178a(24) =191a(25) =206a(26) =220a(27) =235a(28) =251a(29) =267