%I #14 Apr 22 2014 09:56:21
%S 1,3,5,9,12,16,21,27,33,40,47,55,63,70,77,89,101,110,123,134,146,159,
%T 171,186,200,214,229,245,260,275,293,312,329,349,369,388,411,432,451,
%U 474,496,519,542,564,586,611,635,660,689,713
%N Number of distinct integers of the form i+(i+1)+(i+2)+...+j, for 1 <= i <= j <= n.
%C See also A001227 = number of ways to write n as difference of triangular numbers. - _M. F. Hasler_, Apr 20 2014
%e a(3) = 5 because the possible integers are 1,2,3=1+2,5=2+3,6=1+2+3.
%K nonn
%O 1,2
%A _Jeffrey Shallit_, Apr 19 2014