21030

Appears in sequences

• a(1) = 5; a(n+1) = a(n)-th nonprime, where nonprimes begin at 0.at n=40A025001
• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 58.at n=4A031736
• Values of m such that N=(am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,7.at n=21A064240
• Values of m such that N=(am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,21.at n=27A064247
• a(n) = Z(S_m; sigma[1](n), sigma[2](n),..., sigma[m](n)) where Z(S_m; x_1,x_2,...,x_m) is the cycle index of the symmetric group S_m and sigma[k](n) is the sum of k-th powers of divisors of n; m=3.at n=17A068020
• a(n) = 25*n^2 + 5.at n=28A158445