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2013 Nordic
1
1
Part of
2013 Nordic
Problems
(1)
perfect square belonging to an integer sequence
Source: Nordic Mathematical Contest 2013 #1
9/23/2017
Let
(
a
n
)
n
≥
1
{(a_n)_{n\ge1}}
(
a
n
)
n
≥
1
be a sequence with
a
1
=
1
{a_1 = 1}
a
1
=
1
and
a
n
+
1
=
⌊
a
n
+
a
n
+
1
2
⌋
{a_{n+1} = \lfloor a_n +\sqrt{a_n}+\frac{1}{2}\rfloor }
a
n
+
1
=
⌊
a
n
+
a
n
+
2
1
⌋
for all
n
≥
1
{n \ge 1}
n
≥
1
, where
⌊
x
⌋
{\lfloor x \rfloor}
⌊
x
⌋
denotes the greatest integer less than or equal to
x
{x}
x
. Find all
n
≤
2013
{n \le 2013}
n
≤
2013
such that
a
n
{a_n}
a
n
is a perfect square
floor function
Perfect Square
number theory
Integer sequence