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Search: id:A124968
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| A124968 |
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Numbers which can be expressed as the ordered sum of 3 squares in 4 or more different ways. |
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+0
1
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| 81, 89, 101, 125, 129, 134, 146, 149, 153, 161, 162, 170, 171, 173, 185, 189, 194, 198, 201, 206, 209, 221, 225, 230, 233, 234, 241, 242, 243, 245, 246, 249, 250, 251, 254, 257, 261, 266, 269, 270, 274, 278, 281, 285, 289, 290, 293, 294, 297, 299, 305, 306
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Subset of A124967.
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EXAMPLE
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a(1)=81 because 81=6^2+6^2+3^2 = 7^2+4^2+4^2 = 8^2+4^2+1^2 = 9^2+0^2+0^2
161=1^2+4^2+12^2=2^2+6^2+11^2=4^2+8^2+9^2=5^2+6^2+10^2, so 161 is in the list.
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MATHEMATICA
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Needs["NumberTheory`NumberTheoryFunctions`"]; Select[Range[325], Length @ OrderedSumOfSquaresRepresentations[3, # ] >= 4 &] (*Chandler*)
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PROGRAM
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(PARI) isA124968(n)={ local(cnt=0, z2) ; for(x=0, floor(sqrt(n)), for(y=x, floor(sqrt(n-x^2)), z2=n-x^2-y^2 ; if( z2>=y^2 && issquare(z2), cnt++ ; ) ; if(cnt >=4, return(1) ) ; ) ; ) ; return(0) ; } { for(n=1, 800, if( isA124968(n), print1(n, ", ") ; ) ; ) ; } (Mathar)
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CROSSREFS
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Cf. A124966-A124971.
Adjacent sequences: A124965 A124966 A124967 this_sequence A124969 A124970 A124971
Sequence in context: A075691 A055390 A089784 this_sequence A044865 A068834 A067521
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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 14 2006
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EXTENSIONS
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Corrected and extended by Ray Chandler (rayjchandler(AT)sbcglobal.net) and R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 29 2006
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