Least k such that 1+2+...+k >= E{1,2,...,n}, where E = 2nd elementary symmetric function.

Terms

a(0) =2a(1) =5a(2) =8a(3) =13a(4) =19a(5) =25a(6) =33a(7) =42a(8) =51a(9) =62a(10) =74a(11) =86a(12) =100a(13) =115a(14) =130a(15) =147a(16) =165a(17) =183a(18) =203a(19) =224a(20) =245a(21) =268a(22) =292a(23) =316a(24) =342a(25) =369a(26) =396a(27) =425a(28) =455a(29) =485