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A124968 Numbers which can be expressed as the ordered sum of 3 squares in 4 or more different ways. 6
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; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Subset of A124967.

LINKS

Robert Price, Table of n, a(n) for n = 1..81953

EXAMPLE

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.

MATHEMATICA

Select[Range[310], Length@PowersRepresentations[#, 3, 2] >= 4 &] (* Ray Chandler, Oct 31 2019 *)

PROG

(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, ", ") ; ) ; ) ; } \\ R. J. Mathar

CROSSREFS

Cf. A124966-A124971.

Sequence in context: A295700 A286898 A184044 * A294577 A044865 A162529

Adjacent sequences:  A124965 A124966 A124967 * A124969 A124970 A124971

KEYWORD

nonn

AUTHOR

Artur Jasinski, Nov 14 2006

EXTENSIONS

Corrected and extended by Ray Chandler and R. J. Mathar, Nov 29 2006

STATUS

approved

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Last modified December 7 20:40 EST 2021. Contains 349589 sequences. (Running on oeis4.)