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Search: id:A067725
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| 0, 9, 24, 45, 72, 105, 144, 189, 240, 297, 360, 429, 504, 585, 672, 765, 864, 969, 1080, 1197, 1320, 1449, 1584, 1725, 1872, 2025, 2184, 2349, 2520, 2697, 2880, 3069, 3264, 3465, 3672, 3885, 4104, 4329, 4560, 4797, 5040, 5289, 5544, 5805, 6072, 6345, 6624
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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Numbers such that 3*(3 + n) is a perfect square. - Alex Healy (blink2826(AT)aol.com), Tj Tullo, Avery Pickford, Sep 20 2004
a(n)=3*A005563 - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 06 2007
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FORMULA
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a(n)=6*n+a(n-1)-3 (with a(1)=0) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 08 2009]
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EXAMPLE
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For n=2, a(2)=6*2+0-3=9; n=3, a(3)=6*3+9-3=24; n=4, a(4)=6*4+24-3=45 [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 08 2009]
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MAPLE
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a:=n->sum(sum(3, j=2..n), k=0..n): seq(a(n), n=1..40); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 30 2007
[seq((n+(n+1)+(n+2))*(n+3), n=0..49)]; - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jun 24 2006
a:=n->sum(sum(3, j=2..n), k=0..n): seq(a(n), n=2..47); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), May 30 2007
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MATHEMATICA
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Select[ Range[10000], IntegerQ[ Sqrt[ 3(3 + # )]] & ]
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CROSSREFS
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Cf. A005563.
Cf. 8: A067728, 7: A067727, 6: A067726, 5: A067724.
Sequence in context: A161449 A063066 A097658 this_sequence A001106 A023551 A022787
Adjacent sequences: A067722 A067723 A067724 this_sequence A067726 A067727 A067728
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KEYWORD
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nonn,new
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 05 2002
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EXTENSIONS
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Edited by N. J. A. Sloane (njas(AT)research.att.com), Sep 14 2008 at the suggestion of R. J. Mathar
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