25758

Appears in sequences

• Numbers k such that k | sigma_3(k) - phi(k)^3.at n=19A055697
• a(n) = 18*(n - 2)*(2*n - 5).at n=27A060787
• Triangle with T(n,k) = k*E(n,k) where E(n,k) are Eulerian numbers A008292.at n=33A065826
• Numbers k such that sigma(k) = bigomega(k) * phi(k).at n=13A067238
• Numbers n such that sigma(n)/phi(n) is prime.at n=37A067780
• Numbers that have exactly seven prime factors counted with multiplicity (A046308) whose digit reversal is different and also has 7 prime factors (with multiplicity).at n=11A109027
• Numbers n such that sigma(n) = 7*phi(n).at n=9A136540
• A triangle sequence from a sum: t0(n,m)=(2 + PartitionsQ[n] - PartitionsQ[m] - PartitionsQ[n - m]); t1(n,k)=Sum[(-1)^j *t0[n + 1, j](k + 1 - j)^n, {j, 0, k + 1}]; t(n,m)=If[n == 0, 1, t1(n, k) + t1(n, n - k)].at n=22A156130
• A triangle sequence from a sum: t0(n,m)=(2 + PartitionsQ[n] - PartitionsQ[m] - PartitionsQ[n - m]); t1(n,k)=Sum[(-1)^j *t0[n + 1, j](k + 1 - j)^n, {j, 0, k + 1}]; t(n,m)=If[n == 0, 1, t1(n, k) + t1(n, n - k)].at n=26A156130
• Number of four-prime Carmichael numbers less than 10^n.at n=17A174612
• Number of 4X2 integer matrices with each row summing to zero, row elements in nondecreasing order, rows in lexicographically nondecreasing order, and the sum of squares of the elements <= 2*n^2 (number of collections of 4 zero-sum 2-vectors with total modulus squared not more than 2*n^2, ignoring vector and component permutations).at n=34A192703
• a(n) = prime(n)*prime(n+1) + prime(n+2).at n=36A292926
• Number of twice-partitions of n with no singletons.at n=18A358828