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Search: id:A068624
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| A068624 |
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a(1) = 9; a(n+1) = smallest triangular number > a(n) formed by adding at least one digit to a(n). |
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+0
4
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| 9, 91, 1891, 18915, 1989015, 199890015, 19998900015, 1999989000015, 199999890000015, 19999998900000015, 1999999989000000015, 199999999890000000015, 19999999998900000000015
(list; graph; listen)
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OFFSET
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1,1
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FORMULA
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For n>=4, a(n) = 2*10^(2n-4) - 11*10^(n-2) + 15 [From Max Alekseyev (maxale(AT)gmail.com), Apr 25 2009]
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CROSSREFS
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Cf. A068618, A068619, A068621, A068622, A068623.
Sequence in context: A123792 A022520 A020236 this_sequence A034666 A022505 A164913
Adjacent sequences: A068621 A068622 A068623 this_sequence A068625 A068626 A068627
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KEYWORD
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base,more,nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Feb 25 2002
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EXTENSIONS
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3 more terms from Ray G. Opao (1260(AT)email.com), Dec 09 2004
Extended by Max Alekseyev (maxale(AT)gmail.com), Apr 25 2009
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