24601

Appears in sequences

• Hyperperfect numbers: k = m*(sigma(k) - k - 1) + 1 for some m > 1.at n=12A007592
• Hyperperfect numbers: x such that x = 1 + k*(sigma(x)-x-1) for some k > 0.at n=16A034897
• Numbers k such that sopfr(k) = sopfr(k + sopfr(k)).at n=26A050780
• a(n) = a(n-1) + a(n-2) + a(n-3) + R(a(n-4)) where a(0)=a(1)=a(2)=a(3)=1 and R(n) (A004086) is the reverse of n.at n=17A074863
• Apocalypse primes: 10^665+a(n) has 666 decimal digits and is prime.at n=13A115983
• Semiprimes pq with pq - 1 divisible by p + q.at n=8A164643
• Number of 2 X 2 nonsingular 0..n matrices with rows in increasing order.at n=13A183761
• Number of ways to reciprocally link elements of a 2 X n array either to themselves or to exactly two horizontal, diagonal or antidiagonal neighbors.at n=9A220726
• Unitary hyperperfect numbers.at n=19A225150
• Indices of squares of primes in A098550.at n=38A251240
• Bi-unitary k-hyperperfect numbers: numbers m such that m = 1 + k * (bsigma(m) - m - 1) where bsigma(m) is the sum of bi-unitary divisors of m (A188999) and k >= 1 is an integer.at n=14A309568
• Numbers k such that k divides 2^(2*k+1) - 1.at n=6A319538
• Expansion of e.g.f. exp(-2*x)/(exp(-x) - x)^3.at n=5A379990
• The number of n-free abundant numbers below the least number k that is not n-free whose sum of n-free divisors is larger than 2*k.at n=3A387155
• Centered 30-gonal numbers.at n=40A389799