2560001

Appears in sequences

• Semiprimes of the form n^4 + 1.at n=22A186688
• a(n) = 1 + sigma(n)^4.at n=26A259308
• a(1) = 2, a(n) = k + 1, where k is the least number greater than a(n-1) such that rad(k) | a(n-1), where rad(n) = A007947(n).at n=30A365324