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Search: id:A125725
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| A125725 |
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Numbers whose base 7 representation is 222....2. |
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+0
1
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| 0, 2, 16, 114, 800, 5602, 39216, 274514, 1921600, 13451202, 94158416, 659108914, 4613762400, 32296336802, 226074357616, 1582520503314, 11077643523200, 77543504662402, 542804532636816, 3799631728457714, 26597422099204000
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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a(n)=2*(7^n-1)/6.
a(n)=7*a(n-1)+2 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Oct 30 2009]
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EXAMPLE
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base 7.......decimal
0..................0
2..................2
22................16
222..............114
2222.............800
22222...........5602
222222.........39216
2222222.......274514
22222222.....1921600
222222222...13451202
etc...........etc.
For n=2, a(2)=7*0+2=2; n=3, a(3)=7*2+2=16; n=4, a(4)=7*16+2=114 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Oct 30 2009]
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MAPLE
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seq(2*(7^n-1)/6, n=0..20);
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CROSSREFS
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Sequence in context: A117627 A117628 A037564 this_sequence A162723 A159324 A088755
Adjacent sequences: A125722 A125723 A125724 this_sequence A125726 A125727 A125728
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KEYWORD
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easy,nonn
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AUTHOR
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Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Feb 02 2007
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