176017

Properties

Appears in sequences

• Number of ways that a 1 X n rectangular tile T, marked into n unit squares, can be surrounded by one layer of copies of itself laid in the plane grid generated by the units of T. Ways that differ by rotation or reflection are not counted as different. The surrounded tile is the exact surrounded region.at n=33A159294
• Primes p such that A008472(p-1) = A008472(p+1), where A008472 = sum of distinct primes dividing n.at n=13A203182
• Prime numbersat n=15992