OFFSET
1,1
FORMULA
The monotonic ordering of the numbers in the set S generated by these rules: 2 is in S, and if n is in S, then (n^2+5n+2)/2 and n+Floor(1/2+sqrt(2n+4)) are in S.
MATHEMATICA
nn=200; t={2}; t0=t; While[t=Select[Union[t, (1/2)*(t^2+5t+2), t+Floor[1/2+(2t+4)^(1/2)]], #<=nn&]; t0 !t, t0=t]; t
f[s_List] := Select[ Union@ Join[s, (s^2 + 5 s + 2)/2, s + Floor[1/2 + Sqrt@ (2 s + 4)]], # < 201 &]; NestWhile[f, {2}, UnsameQ, All]
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jan 02 2011
STATUS
approved