A214858 Natural numbers missing from A214857.
5, 8, 12, 15, 19, 22, 26, 29, 32, 36, 39, 43, 46, 49, 53, 56, 60, 63, 67, 70, 73, 77, 80, 84, 87, 90, 94, 97, 101, 104, 108, 111, 114, 118, 121, 125, 128, 131, 135, 138, 142, 145, 149, 152, 155, 159, 162, 166, 169, 172, 176, 179, 183, 186, 189, 193, 196, 200
Offset: 1
Programs
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Mathematica
tri = Table[n (n + 1)/2, {n, 0, 1000}]; t = Table[Count[tri, ?(# <= n^2 &)], {n, 0, Sqrt[tri[[-1]]]}]; Complement[Range[t[[-1]]], t] (* _T. D. Noe, Mar 11 2013 *)
Formula
a(n+1) - a(n) = 3 or 4.
Extensions
Extended by T. D. Noe, Mar 11 2013