A069699 - OEIS

%I #6 Dec 05 2013 19:55:17

%S 0,1,3,6,10,15,21,28,36,45,55,66,78,91,171,276,378,1770,2775,5778,8778

%N Triangular numbers with internal digits 7.

%C For proof of finiteness see A069693.

%t Do[ If[ Union[ Drop[ RotateLeft[ IntegerDigits[n(n + 1)/2]], -2]] == {6}, Print[n(n + 1)/2]], {n, 14, 2 10^6}]

%Y Cf. A069675 to A069684, A069693 to A069700.

%K nonn,base,fini,full

%O 1,3

%A _Amarnath Murthy_, Apr 06 2002

%E Corrected by _Sascha Kurz_, Jan 02 2003