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Search: id:A069702
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| A069702 |
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Triangular numbers with internal digits also forming a triangular number > 0. |
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+0
1
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| 105, 136, 210, 231, 300, 406, 435, 465, 561, 630, 666, 703, 861, 903, 1035, 2016, 2211, 2556, 3003, 3916, 4005, 5151, 6105, 6216, 6555, 6786, 8001, 8911, 9453, 10011, 10153, 19900, 20100, 20910, 23005, 28203, 39903, 41905, 46665, 48205
(list; graph; listen)
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OFFSET
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0,1
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EXAMPLE
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3916 is a member as 3916 and 91 both are triangular.
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MATHEMATICA
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s=Select[Range[14, 400], IntegerQ[Sqrt[1+8FromDigits[Drop[Drop[IntegerDigits[ #(#+1)/2], 1], -1]]]]&]; s(s+1)/2
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CROSSREFS
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Sequence in context: A095643 A097217 A115935 this_sequence A133509 A013590 A046389
Adjacent sequences: A069699 A069700 A069701 this_sequence A069703 A069704 A069705
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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 06 2002
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EXTENSIONS
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Edited by Dean Hickerson (dean(AT)math.ucdavis.edu), Apr 09 2002
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