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Search: id:A069790
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| A069790 |
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Triangular numbers with arithmetic mean of digits = 1 (sum of digits = number of digits). |
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+0
2
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| 1, 120, 210, 300, 112101, 100600020, 101111310, 110120220, 200130021, 200310120, 1000051003, 1010004040, 1130002030, 1411000003, 2002021003, 3200200003, 5000050000, 100110002070, 111111101310, 111202101003
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The sum of the digits of a triangular number is 0, 1, 3 or 6 (mod 9).
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MATHEMATICA
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s=Select[Range[500000], Length[z=IntegerDigits[ #(#+1)/2]]==Plus@@z&]; s(s+1)/2
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CROSSREFS
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Sequence in context: A054572 A056994 A114823 this_sequence A064224 A069674 A003015
Adjacent sequences: A069787 A069788 A069789 this_sequence A069791 A069792 A069793
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KEYWORD
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base,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 08 2002
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EXTENSIONS
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Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com) and Robert G. Wilson v (rgwv(AT)rgwv.com), Apr 10 2002
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