42718

Appears in sequences

• Numbers k such that sopf(k) = sopf(k+2), where sopf(k) = A008472(k).at n=29A063968
• A089450 indexed by A000040.at n=21A089525
• Quintuple primorial n##### = n#5.at n=16A114421
• 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=21A159294
• a(n) = Sum_{k=1..n-1} k^2*phi(k) + n^2*phi(n)/2, where phi = A000010.at n=21A333293