%I #10 Oct 10 2019 03:58:47
%S 10,11,13,16,1110,1115,1211,1218,1316,1415,25,26,1718,1911,111015,
%T 111210,111316,111513,111711,111910,121110,121311,121513,121716,1320,
%U 131215,131511,131718,141016,141315,141615,141916,151218,151611,151915
%N Describe the n-th triangular number A000217(n).
%Y Cf. A000217, A005150, A045987, A045988.
%K nonn,easy,base
%O 0,1
%A _N. J. A. Sloane_
%E More terms from _Patrick De Geest_, Jun 15 1999