<s>
In	O
linear	B-Language
algebra	I-Language
,	O
a	O
heptadiagonal	B-Algorithm
matrix	I-Algorithm
is	O
a	O
matrix	B-Architecture
that	O
is	O
nearly	O
diagonal	B-Algorithm
;	O
to	O
be	O
exact	O
,	O
it	O
is	O
a	O
matrix	B-Architecture
in	O
which	O
the	O
only	O
nonzero	O
entries	O
are	O
on	O
the	O
main	O
diagonal	B-Algorithm
,	O
and	O
the	O
first	O
three	O
diagonals	O
above	O
and	O
below	O
it	O
.	O
</s>
<s>
It	O
follows	O
that	O
a	O
heptadiagonal	B-Algorithm
matrix	I-Algorithm
has	O
at	O
most	O
nonzero	O
entries	O
,	O
where	O
n	O
is	O
the	O
size	O
of	O
the	O
matrix	B-Architecture
.	O
</s>
<s>
Hence	O
,	O
heptadiagonal	O
matrices	O
are	O
sparse	B-Algorithm
.	O
</s>
<s>
This	O
makes	O
them	O
useful	O
in	O
numerical	B-General_Concept
analysis	I-General_Concept
.	O
</s>
