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Search: id:A069693
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| A069693 |
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Triangular numbers with either no internal digits or all internal digits are 0. |
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+0
8
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| 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 300, 406, 703, 903, 3003, 4005, 8001
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Is the sequence finite?
There are no other values <= 10^50. - Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Jan 02 2003
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EXAMPLE
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The internal digits of 3003 are "00", which are both 0. 15 has no internal digits.
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MATHEMATICA
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Do[ If[ Union[ Drop[ RotateLeft[ IntegerDigits[n(n + 1)/2]], -2]] == {0}, Print[n(n + 1)/2]], {n, 14, 2 10^6}]
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CROSSREFS
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Cf. A069675-A069684, A069693-A067000.
Adjacent sequences: A069690 A069691 A069692 this_sequence A069694 A069695 A069696
Sequence in context: A077367 A077366 A077368 this_sequence A069694 A069695 A069697
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KEYWORD
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nonn,base
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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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Corrected by Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Jan 02 2003
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