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Search: id:A062725
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| A062725 |
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Write 0,1,2,3,4,... in a triangular spiral, then a(n) is the sequence found by reading the line from 0 in the direction 0,7,... |
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+0
2
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| 0, 7, 23, 48, 82, 125, 177, 238, 308, 387, 475, 572, 678, 793, 917, 1050, 1192, 1343, 1503, 1672, 1850, 2037, 2233, 2438, 2652, 2875, 3107, 3348, 3598, 3857, 4125, 4402, 4688, 4983, 5287, 5600, 5922, 6253, 6593, 6942, 7300, 7667, 8043, 8428, 8822, 9225
(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) = n*(9n+5)/2
a(n)=9*n+a(n-1)-11 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 12 2009]
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EXAMPLE
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The spiral begins:
..........15
........16..14
......17..3...13
....18..4...2...12
..19..5...0...1...11
20..6...7...8...9...10
For n=2, a(2)=9*2+0-11=7; n=3, a(3)=9*3+7-11=23; n=4, a(4)=9*4+23-11=48 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 12 2009]
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MATHEMATICA
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s=0; lst={s}; Do[s+=n++ +7; AppendTo[lst, s], {n, 0, 7!, 9}]; lst [From Vladimir Orlovsky (4vladimir(AT)gmail.com), Nov 16 2008]
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CROSSREFS
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Cf. A051682.
Sequence in context: A158035 A101789 A162290 this_sequence A147121 A098334 A038796
Adjacent sequences: A062722 A062723 A062724 this_sequence A062726 A062727 A062728
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KEYWORD
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nonn,easy
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AUTHOR
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Floor van Lamoen (fvlamoen(AT)hotmail.com), Jul 21 2001
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