A120930 Least x satisfying n^3 + x^3 + y^3 = z^3, where (n,x,y,z),n<x<y<z forms a primitive quadruple.

6, 17, 4, 17, 76, 32, 14, 209, 55, 261, 15, 19, 51, 23, 42, 23, 40, 19, 53, 54, 43, 51, 81, 159, 31, 55, 30, 53, 34, 266, 33, 54, 70, 39, 77, 38, 174, 43, 146, 141, 114, 83, 230, 51, 53, 47, 75, 85, 80, 61, 82, 321, 58, 80, 113, 61, 68, 59, 93, 342, 90, 183, 228, 75, 87, 97

Offset

1,1

Comments

There are a few small cases where the least x needs y>1000, e.g. 8^3+209^3+1744^3=1745^3. The S. Dutch link has a few nonprimitive quartets which have to be excluded for this sequence, e.g. 37^3+222^3+296^3=333^3. - Martin Fuller, Aug 11 2006

Links

Table of n, a(n) for n=1..66.

S. Dutch, Cubic Quartets With a,b,c<1000

Prog

(PARI) A(n)=local(x, y, z); x=n+1; while(1, y=x+1; while(n^3+x^3+y^3>=(y+1)^3, if(ispower(n^3+x^3+y^3, 3, &z) && (gcd([n, x, y, z])==1), return(x)); y++; ); x++; ); \\ Martin Fuller, Aug 11 2006

Crossrefs

Cf. A120931, A120932.

Sequence in context: A022510 A065776 A323516 * A070395 A200871 A112366

Adjacent sequences: A120927 A120928 A120929 * A120931 A120932 A120933

Keyword

nonn

Author

Lekraj Beedassy, Jul 16 2006

Extensions

Corrected by R. J. Mathar, Nov 25 2006

Status

approved