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A068128 Triangular numbers with sum of digits = 6. 6
6, 15, 105, 231, 2211, 3003, 20301, 112101, 2003001, 122000010, 200030001, 20000300001, 2000003000001, 200000030000001, 20000000300000001, 2000000003000000001, 200000000030000000001, 20000000000300000000001, 2000000000003000000000001 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
COMMENTS
1. The sequence is unbounded, as the (2*10^k +1)-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.
LINKS
MATHEMATICA
Select[Accumulate[Range[20000002]], Total[IntegerDigits[#]]==6&] (* Harvey P. Dale, Jun 05 2012 *)
CROSSREFS
Cf. A068127.
Sequence in context: A194265 A129521 A029765 * A013222 A013228 A133472
KEYWORD
base,easy,nonn
AUTHOR
Amarnath Murthy, Feb 21 2002
EXTENSIONS
More terms from Sascha Kurz, Mar 06 2002
More terms from Sean A. Irvine, Mar 17 2023
STATUS
approved

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Last modified March 3 10:19 EST 2024. Contains 370510 sequences. (Running on oeis4.)