A069699 Triangular numbers with internal digits 7.

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

Offset: 1

Author

Amarnath Murthy, Apr 06 2002

Keywords

• nonn
• base
• fini
• full

Comments

For proof of finiteness see A069693.

Crossrefs

Cf. A069675 to A069684, A069693 to A069700.

Programs

Mathematica

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

Extensions

Corrected by Sascha Kurz, Jan 02 2003