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 A124971 Numbers n which can be expressed as the ordered sum of 3 squares in 2 or more different ways and such that n+1 has the same property. 6
 17, 25, 26, 33, 49, 50, 53, 61, 65, 68, 72, 73, 74, 81, 82, 85, 89, 97, 98, 99, 100, 101, 104, 105, 106, 107, 108, 109, 113, 116, 117, 121, 122, 125, 129, 130, 131, 136, 137, 138, 144, 145, 146, 149, 152, 153, 154, 157, 161, 164, 165, 169, 170, 173, 177, 178 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS R. J. Mathar, Table of n, a(n) for n = 1..6598 FORMULA A000164(n)>=2 and A000164(n+1)>=2. - R. J. Mathar, Nov 29 2006 EXAMPLE a(1)=17 because 17=3^2+2^2+2^2 = 4^2+1^2+0^2 and a(1)+1= 18=3^2+3^2+0^2 = 4^2+1^2+1^2 MATHEMATICA Needs["NumberTheory`NumberTheoryFunctions`"]; Select[Range[185], Length @ OrderedSumOfSquaresRepresentations[3, # ] > 1 && Length @ OrderedSumOfSquaresRepresentations[3, # + 1] > 1 &] (*Chandler*) PROG (PARI) isCnt3sqr(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 >=2, return(1) ) ; ) ; ) ; return(0) ; } isA124971(n)= { return( isCnt3sqr(n) && isCnt3sqr(n+1)) ; } { for(n=1, 200, if( isA124971(n), print1(n, ", ") ; ) ; ) ; } - R. J. Mathar, Nov 29 2006 CROSSREFS Cf. A124966-A124970. Sequence in context: A231963 A158803 A051780 * A272635 A105448 A082130 Adjacent sequences:  A124968 A124969 A124970 * A124972 A124973 A124974 KEYWORD nonn AUTHOR Artur Jasinski, Nov 14 2006 EXTENSIONS Corrected and extended by Ray Chandler, Nov 30 2006 Corrected and extended by R. J. Mathar, Nov 29 2006 STATUS approved

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Last modified January 18 10:53 EST 2019. Contains 319271 sequences. (Running on oeis4.)