It can be shown that the positive integers representable as the sum of two squares and one power of k (k any fixed integer ≥ 2) have positive density, from which it follows that those integers representable as the sum of two squares and (at most) two powers of k also have positive density. The purpose of this paper is to show that there is an infinity of positive integers not representable as the sum of two squares and two (or fewer) powers of k, k again any fixed integer ≥ 2.
@article{bwmeta1.element.bwnjournal-article-doi-10_4064-cm112-2-3,
author = {Roger Clement Crocker},
title = {On the sum of two squares and two powers of k},
journal = {Colloquium Mathematicae},
volume = {111},
year = {2008},
pages = {235-267},
zbl = {1173.11051},
language = {en},
url = {http://dml.mathdoc.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm112-2-3}
}
Roger Clement Crocker. On the sum of two squares and two powers of k. Colloquium Mathematicae, Tome 111 (2008) pp. 235-267. http://gdmltest.u-ga.fr/item/bwmeta1.element.bwnjournal-article-doi-10_4064-cm112-2-3/