OFFSET
0,7
LINKS
Eric Weisstein's World of Mathematics, Centered Square Number
EXAMPLE
a(19) = 6 because we have [13, 5, 1], [13, 1, 5], [5, 13, 1], [5, 1, 13], [1, 13, 5] and [1, 5, 13].
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Feb 04 2020
STATUS
approved