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Search: id:A124980
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| A124980 |
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Smallest strictly positive number decomposable in n different ways as a sum of two squares. |
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+0
2
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| 1, 25, 325, 1105, 4225, 5525, 203125, 27625, 71825, 138125
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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a(3)=325 3-th term 325 is decomposable on 3 ways: 15^2+10^2 = 17^2+6^2 = 18^2+1^2
a(n)=A000446(n), n>1. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 15 2008
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PROGRAM
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(PARI) cnt2sqr(n)={local(cnt=0, y2) ; for(x=0, floor(sqrt(n)), y2=n-x^2 ; if( y2>=x^2 && issquare(y2), cnt++ ; ) ; ) ; return(cnt) ; } A124980(n)= { local(a=1) ; while(1, if( cnt2sqr(a)==n, return(a) ; ) ; a++ ; ) ; } { for(n=1, 100, print(n, " ", A124980(n)) ; ) ; } - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 29 2006
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CROSSREFS
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Cf. A118882.
Sequence in context: A020233 A020319 A000448 this_sequence A000446 A079875 A162702
Adjacent sequences: A124977 A124978 A124979 this_sequence A124981 A124982 A124983
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KEYWORD
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nonn
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Nov 15 2006
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 29 2006
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