

A240775


The six values n in each interval [i*840, (i+1)*840), where i >= 0, for which Mordell's formulas do NOT provide a threeEgyptianfraction solution for 4/n.


1




OFFSET

1,2


COMMENTS

ErdÅ‘s and Straus conjectured that for all integers n >= 2, the rational number 4/n can be expressed as an Egyptian fraction with exactly three unit fractions  that is, 4/n = 1/x + 1/y + 1/z where x, y and z are positive integers. The conjecture has been verified to high values of n, and Mordell has provided formulas to compute x, y and z for many n. The values of n NOT included in Mordell's formulas are those for which n modulo 840 = {an element of this sequence}. Each element is the square of a prime.


REFERENCES

Louis J. Mordell, Diophantine Equations, Academic Press, 1967, 287290.


LINKS

Table of n, a(n) for n=1..6.


CROSSREFS

Sequence in context: A262514 A258693 A037266 * A284643 A074730 A268519
Adjacent sequences: A240772 A240773 A240774 * A240776 A240777 A240778


KEYWORD

nonn,fini,full


AUTHOR

Kenneth Vollmar, Apr 12 2014


STATUS

approved



