A254324 Least Y such that X^3 + Y^3 = A020898(n)*Z^3 for some X <= Y and some Z.

1, 37, 5, 2, 89, 7, 683

Offset

1,2

Comments

Also, max {X,Y,Z} for the smallest (in this sense of this sup norm) positive integer solution (X,Y,Z) to X^3 + Y^3 = A020898(n)*Z^3.

The X values are given in A254326.

a(8) > 10^5, with A020898(8)=17. Then the sequence continues a(9,10,...) = 5, 19, ?, 75, 3, 163, ?, 1853, ?, 3, 19, ...

Links

Table of n, a(n) for n=1..7.

Example

A020898(1)=2 and 1^3 + 1^3 = 2*1^3, therefore a(1)=1.
A020898(2)=6 and 17^3 + 37^3 = 6*21^3, and there is no "smaller" solution (with X, Y, Z < 37), therefore a(2)=37.

Prog

(PARI) a(n, L=10^9)={n=if(n>0, A020898[n], -n); for(b=1, L, for(a=1, b, (a^3+b^3)%n&&next; ispower((a^3+b^3)/n, 3)&&return(b)))}

Crossrefs

Cf. A020898, A254326.

Sequence in context: A278067 A178199 A107812 * A356745 A068843 A284497

Adjacent sequences: A254321 A254322 A254323 * A254325 A254326 A254327

Keyword

nonn,more

Author

M. F. Hasler, Jan 27 2015

Status

approved