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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 Table of n, a(n) for n=0..18. 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 Adjacent sequences: A068125 A068126 A068127 * A068129 A068130 A068131 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.)