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Search: id:A159693
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| 1, 2, 4, 8, 11, 20, 24, 40, 45, 70, 76, 112, 119, 168, 176, 240, 249, 330, 340, 440, 451, 572, 584, 728, 741, 910, 924, 1120, 1135, 1360, 1376, 1632, 1649, 1938, 1956, 2280, 2299, 2660, 2680, 3080, 3101, 3542, 3564, 4048, 4071, 4600, 4624, 5200, 5225, 5850
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OFFSET
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1,2
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COMMENT
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Sum of integers followed by squares
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FORMULA
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a(n)=(n^3+3*n^2+8*n+IFTE(n MOD 2 = 1, 3*n+9, 3*n^2))/24
a(n)=a(n-1)+3*a(n-2)-3*a(n-3)-3*a(n-4)+3*a(n-5)+a(n-6)-a(n-7). G.f.: x*(1+x-x^2+x^3)/((1+x)^3*(x-1)^4). [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 20 2009]
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EXAMPLE
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For n=9, a(n)=1+1+2+4+3+9+4+16+5=45
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PROGRAM
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(MAGMA) S:=&cat[ [ n, n^2 ]: n in [1..25] ]; [ n eq 1 select S[1] else Self(n-1)+S[n]: n in [1..#S] ]; [From Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Apr 20 2009]
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CROSSREFS
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Sequence in context: A007295 A053439 A033956 this_sequence A053437 A018277 A004654
Adjacent sequences: A159690 A159691 A159692 this_sequence A159694 A159695 A159696
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KEYWORD
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nonn
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AUTHOR
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Gerald Hillier (adr.rabbicat(AT)gmail.com), Apr 20 2009
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl) and Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), Apr 20 2009
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