A068129 Triangular numbers with sum of digits = 10.

28, 55, 91, 136, 190, 253, 325, 406, 703, 820, 1081, 1225, 1540, 1711, 2080, 2701, 3160, 3403, 5050, 7021, 10153, 11026, 12403, 15400, 17020, 20503, 21115, 23005, 24310, 32131, 41041, 51040, 52003, 60031, 72010, 80200, 90100, 106030, 110215

Offset

0,1

Comments

1. The sequence is unbounded, as the (2*10^k +2)-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.

The second assertion above is wrong. Out of the first 100,000 triangular numbers, only 26,046 have a sum of their digits equal to a triangular number. - Harvey P. Dale, Jun 07 2017

Links

Table of n, a(n) for n=0..38.

Mathematica

Select[Accumulate[Range[1000]], Total[IntegerDigits[#]]==10&] (* Harvey P. Dale, Jun 07 2017 *)

Crossrefs

Cf. A068127, A068128.

Sequence in context: A056028 A120372 A274642 * A079731 A119168 A040756

Adjacent sequences: A068126 A068127 A068128 * A068130 A068131 A068132

Keyword

base,easy,nonn

Author

Amarnath Murthy, Feb 21 2002

Extensions

More terms from Sascha Kurz, Mar 06 2002

Status

approved