%I
%S 0,1,3,5,6,10,11,15,16,20,21,25,26,28,30,31,35,36,40,41,45,46,50,51,
%T 53,55,56,60,61,65,66,70,71,75,76,78,80,81,85,86,90,91,95,96
%N Triangular numbers n*(n+1)/2 mod 100, sorted and uniqued.
%C Possible last two digits of triangular numbers n*(n+1)/2 (leading zeros omitted).
%C All triangular numbers less than 100 belong to this sequence; the sequence is finite with 44 terms: a(44)=96 is the last term.
%e The last two digits of n*(n+1)/2 can be: 00, 01, 03, 20, 91, etc... but not 02, 04, 12, 97 etc...
%t Union[Table[Mod[n*(n + 1)/2, 100], {n, 1, 100}]]
%Y Cf. A000217, A010461.
%K base,fini,full,nonn
%O 1,3
%A _Shyam Sunder Gupta_, Aug 30 2013
