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Search: id:A122931
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| 1, 2, 7, 18, 50, 132, 351, 924, 2431, 6380, 16732, 43848, 114869, 300846, 787815, 2062830, 5401054, 14140940, 37022755, 96928920, 253766591, 664375032, 1739365272, 4553731728, 11921847625, 31211839802, 81713718151, 213929389674
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OFFSET
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1,2
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COMMENT
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Also sums of the natural numbers with A000045 entries per row: for example 1 2 3+4 5+6+7 8+9+10+11+12.
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FORMULA
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a(n)=sum_{i=A000071(n+1)+1..A000071(n+2)} i. a(n)=A000045(n)*[A000071(n+1)+{A000045(n)+1}/2]. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 07 2006
a(n) = Sum_{k=1..n} [A000045(k)^2*A000045(n-k+1)] - Gerald McGarvey (gerald.mcgarvey(AT)comcast.net), Nov 08 2007
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MAPLE
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A000045 := proc(n) if n <= 1 then RETURN(n) ; else RETURN( A000045(n-1)+A000045(n-2)) ; fi ; end: A000071 := proc(n) RETURN(A000045(n)-1) ; end: A122931 := proc(n) local a45 ; a45 := A000045(n) ; RETURN (a45*(A000071(n+1)+(a45+1)/2)) ; end: for n from 1 to 30 do printf("%d, ", A122931(n)) ; od ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 07 2006
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CROSSREFS
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Cf. A000027 A000045 A001654 A003714 A010049 A035514 A122930.
Sequence in context: A017925 A030236 A074141 this_sequence A094976 A006869 A099626
Adjacent sequences: A122928 A122929 A122930 this_sequence A122932 A122933 A122934
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KEYWORD
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easy,nonn
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AUTHOR
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Alford Arnold (Alford1940(AT)aol.com), Sep 20 2006
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Oct 07 2006
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