A068130 Triangular numbers with sum of digits = 15.

78, 276, 465, 528, 780, 861, 1176, 1275, 1653, 1770, 2346, 2850, 3570, 3741, 4371, 4560, 5253, 5460, 6216, 6441, 7260, 7503, 11175, 12246, 12561, 14028, 15225, 17205, 20706, 22155, 24090, 24531, 26106, 28203, 30381, 32640, 33153, 35511

Offset: 1

Author

Amarnath Murthy, Feb 21 2002

Keywords

• base
• easy
• nonn

Comments

1. The sequence is unbounded, as the (2*10^k +3)-th triangular number is a term. 2. The sum of the digits of triangular numbers in most cases is a triangular number. 3. Conjecture: For every triangular number T there exist infinitely many triangular numbers with sum of digits = T.

Crossrefs

Cf. A068127, A068128, A068129.

Programs

Mathematica

Select[Accumulate[Range[300]],Total[IntegerDigits[#]]==15&] (* Harvey P. Dale, Oct 09 2012 *)

Extensions

More terms from Sascha Kurz, Mar 06 2002