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Search: id:A064694
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| A064694 |
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Add column entries of the table with rows (1,2,0,0...), (0,3,4,5,0,0...), (0,0,6,7,8,9,0,0...), (0,0,0,10,11,12,13,14,0,0...), ... |
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+0
1
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| 1, 5, 10, 22, 34, 58, 80, 120, 155, 215, 266, 350, 420, 532, 624, 768, 885, 1065, 1210, 1430, 1606, 1870, 2080, 2392, 2639, 3003, 3290, 3710, 4040, 4520, 4896, 5440, 5865, 6477, 6954, 7638, 8170, 8930, 9520, 10360, 11011, 11935, 12650, 13662, 14444
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(2n-1)=n(n+1)(7n-4)/6=A007584, a(2n)=n(n+1)(7n+8)/6
a(n)=sum{k=0..floor((n+1)/2), (n-k+1)ceiling((n-k+1)/2)+k+if(mod(n-k+1, 2) =0, ceiling((n-k+1)/2), 0)}. - Paul Barry (pbarry(AT)wit.ie), Aug 25 2004
a(n)=sum{k=0..floor(n/2), C(n-k+1,2)+k}; - Paul Barry (pbarry(AT)wit.ie), Jul 23 2008
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EXAMPLE
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a(1)=1, a(2)=2+3=5, a(3)=4+6=10, a(4)=5+7+10=22
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CROSSREFS
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A007584.
Sequence in context: A132174 A132461 A087746 this_sequence A067622 A098112 A037240
Adjacent sequences: A064691 A064692 A064693 this_sequence A064695 A064696 A064697
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KEYWORD
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easy,nice,nonn
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AUTHOR
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Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de), Oct 12 2001
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