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Search: id:A085905
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| A085905 |
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Permanent of the symmetric n X n matrix M defined by M(i,j) = lcm(i,j) for 1 <= i,j <= n. |
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+0
1
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| 1, 6, 144, 5952, 772560, 73664640, 29745273600, 8715934402560, 5068085799813120, 2756328707949465600, 4581860819083475558400, 2696083278990328597708800, 7844679216026128507826995200
(list; graph; listen)
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OFFSET
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1,2
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EXAMPLE
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a(2)=6 since the 2 by 2 matrix A with rows [1,2],[2,2] has permanent 1*2+2*2=6.
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MAPLE
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with(linalg): a:=(i, j)->lcm(i, j): seq(permanent(matrix(n, n, a)), n=1..14); (Deutsch)
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PROGRAM
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(PARI) permRWNb(a)=n=matsize(a)[1]; if(n==1, return(a[1, 1])); sg=1; in=vectorv(n); x=in; x=a[, n]-sum(j=1, n, a[, j])/2; p=prod(i=1, n, x[i]); for(k=1, 2^(n-1)-1, sg=-sg; j=valuation(k, 2)+1; z=1-2*in[j]; in[j]+=z; x+=z*a[, j]; p+=prod(i=1, n, x[i], sg)); return(2*(2*(n%2)-1)*p) for(n=1, 20, a=matrix(n, n, i, j, lcm(i, j)); print1(permRWNb(a)", ")) - Herman Jamke (hermanjamke(AT)fastmail.fm), May 14 2007
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CROSSREFS
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Cf. A060238, A085244, A034444.
Sequence in context: A111839 A128785 A010043 this_sequence A090443 A133460 A166953
Adjacent sequences: A085902 A085903 A085904 this_sequence A085906 A085907 A085908
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KEYWORD
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nonn
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AUTHOR
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Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 16 2003
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EXTENSIONS
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More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 08 2005
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