6320160

Appears in sequences

• Four numbers (a,b,c,d) with a<b<c<d that satisfy sigma(a) = sigma(b) = sigma(c) = sigma(d) = a+b+c+d are called an amicable quadruple. We order these quadruples according to the common value of sigma. The values of (a, b, c, d, sigma) are in (this sequence, A036472, A036473, A036474, A116148) respectively.at n=9A036471
• a(n) = lcm_{k=1..n} (prime(k) + 1).at n=15A085272
• a(n) = lcm_{k=1..n} (prime(k) + 1).at n=16A085272
• Ramanujan's largely composite numbers n (A067128) which are not divisible by all the primes < p, where p is the greatest prime divisor of n.at n=34A273379
• Numbers that are both unitary and nonunitary harmonic numbers.at n=5A348923
• Denominators of the partial sums of the reciprocals of the Dedekind psi function (A001615).at n=42A357819
• Denominators of the partial sums of the reciprocals of the Dedekind psi function (A001615).at n=43A357819
• Denominators of the partial sums of the reciprocals of the Dedekind psi function (A001615).at n=44A357819
• Denominators of the partial sums of the reciprocals of the Dedekind psi function (A001615).at n=45A357819
• Denominators of the partial alternating sums of the reciprocals of the Dedekind psi function (A001615).at n=42A357821
• Denominators of the partial alternating sums of the reciprocals of the Dedekind psi function (A001615).at n=43A357821
• Denominators of the partial alternating sums of the reciprocals of the Dedekind psi function (A001615).at n=44A357821
• Denominators of the partial alternating sums of the reciprocals of the Dedekind psi function (A001615).at n=45A357821
• Numbers k achieving record abundance (sigma(k) > 2*k) via a residue-based measure M(k) (see Comments), analogous to superabundant numbers A004394.at n=29A362081
• For n > 1, if n appears in the sequence, a(n) = a(n-1) - n if nonnegative and not already in the sequence, otherwise a(n) = a(n-1) + n. Otherwise a(n+1) = a(n)/(n+1) if (n+1)|a(n), otherwise a(n)*(n+1), a(1) = 1 and a(2) = 1*2.at n=10A362698
• a(n) = n! / (floor(n/3))! - n! / (floor(n/2))!.at n=11A374648
• Numbers k that have a record number of divisors that have the same binary weight as k.at n=29A381069