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Search: id:A155757
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| A155757 |
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a(n)=n(n-1)+a(n-1), with a(1)=5 |
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+0
1
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| 5, 7, 13, 25, 45, 75, 117, 173, 245, 335, 445, 577, 733, 915, 1125, 1365, 1637, 1943, 2285, 2665, 3085, 3547, 4053, 4605, 5205, 5855, 6557, 7313, 8125, 8995, 9925, 10917, 11973, 13095, 14285, 15545, 16877, 18283, 19765, 21325, 22965
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OFFSET
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1,1
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FORMULA
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a(n)=n(n-1)+a(n-1), with a(1)=5
a(n)=4*a(n-1)-6*a(n-2)+4*a(n-3)-a(n-4) = 5+n(n^2-1)/3 = 5+A007290(n+1). G.f.: x(5-13x+15x^2-5x^3)/(1-x)^4. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 19 2009]
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EXAMPLE
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For n=2, a(2)=2*1+5=7; n=3, a(3)=3*2+7=13; n=4, a(4)=4*3+13=25
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CROSSREFS
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Cf. A155753
Sequence in context: A038901 A155006 A078724 this_sequence A027674 A124307 A158294
Adjacent sequences: A155754 A155755 A155756 this_sequence A155758 A155759 A155760
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KEYWORD
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nonn
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AUTHOR
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Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Jan 26 2009
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