81797

Appears in sequences

• Brilliant numbers such that when they are concatenated with their 10's complement, which also must be brilliant, the result is a prime.at n=10A084629
• Expansion of (1 - 3*x + 2*x^2)/(1 - 4*x + 3*x^2 + x^3).at n=12A121449
• Numbers of the form n^2 + 1 without prime divisors of the form a^2 + 1.at n=27A217279
• G.f.: 1/(1 - x*(1-x^5)/(1 - x^2*(1-x^6)/(1 - x^3*(1-x^7)/(1 - x^4*(1-x^8)/(1 - x^5*(1-x^9)/(1 - ...)))))), a continued fraction.at n=24A227374
• 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=12A365324
• Squarefree terms of A129802 whose prime factors are neither elite (A102742) nor anti-elite (A128852), where A129802 is the possible bases for Pepin's primality test for Fermat numbers.at n=16A372895