67281

Appears in sequences

• q-factorial numbers 3!_q.at n=40A069778
• p(p^2-p+1) as p runs through the primes.at n=12A083558
• a(n) = 80*n^2 + 1.at n=29A158776
• The number of permutations of length n sortable by 3 prefix reversals (in the pancake sorting sense).at n=41A228398
• Compound filter: a(n) = P(sigma(n), sigma(2n)), where P(n,k) is sequence A000027 used as a pairing function, and sigma is the sum of divisors (A000203).at n=55A286359
• Smallest integer m = b*c which satisfies (b + c)*n = m - 1.at n=39A364169
• a(n) = m is the least m = b*c > a(n-1) such that (b+c)*n = m-1 where 1 < b <= c < m.at n=39A364171
• a(n) = Sum_{k=1..n} sigma_2( n/gcd(k,n) ).at n=40A372226