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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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5
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1, 25, 325, 1105, 4225, 5525, 203125, 27625, 71825, 138125, 2640625, 160225, 17850625, 1221025, 1795625, 801125, 1650390625, 2082925, 49591064453125, 4005625, 44890625, 2158203125, 30525625, 5928325, 303460625, 53955078125, 35409725, 100140625
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Ray Chandler, Table of n, a(n) for n = 1..1458 (a(1459) exceeds 1000 digits).
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FORMULA
| 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
a(n) = min(A018782(2n-1),A018782(2n)).
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PROG
| (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
| Cf. A002144, A018782, A054994, A118882.
See A016032, A000446 and A093195 for other versions.
Sequence in context: A020319 A000448 A000446 * A188355 A079875 A162702
Adjacent sequences: A124977 A124978 A124979 * A124981 A124982 A124983
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KEYWORD
| nonn
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AUTHOR
| Artur Jasinski (grafix(AT)csl.pl), Nov 15 2006
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EXTENSIONS
| More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 29 2006
Edited and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jan 07 2012
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