796797

Appears in sequences

• Expansion of 1/((1-3*x)*(1-9*x)).at n=6A016142
• Primitive numbers k that divide sigma(k)*phi(k).at n=25A055196
• Sum of 2nd, 4th, 6th, 8th and 10th powers of divisors are divisible by sum of divisors.at n=23A074471
• Numbers k such that the sum of 2nd, 3rd, 4th and 5th powers of divisors of k are divisible by sum of divisors of k.at n=26A074632
• Infinite lower triangular matrix, M, that satisfies [M^3](i,j) = M(i+1,j+1) for all i,j>=0 where [M^n](i,j) denotes the element at row i, column j, of the n-th power of matrix M, with M(0,k)=1 and M(k,k)=1 for all k>=0.at n=42A078122
• Number of preferential arrangements of n labeled elements where the exchange of elements among the levels is restricted to levels of different occupation numbers.at n=10A122404
• Pentagonal numbers > 0 which are not the difference of two other pentagonal numbers > 0.at n=30A135769
• a(n) = Sum_{d|n} Moebius(n/d)*d^(b-1)/phi(n) for b = 8.at n=8A160897
• Expansion of x^2/((3*x-1)*(3*x^2-1)).at n=14A167993
• Integers m such that A240923(m) = 1, where A240923(n) = numerator(sigma(n)/n) - sigma(denominator(sigma(n)/n)).at n=20A240991
• a(n) = n^2*(3*n^2 - 1)/2.at n=27A260810
• Numbers k having at least one prime factor p such that p^2 divides 2^(k-1) - 1.at n=3A291194
• Odd numbers k that have a divisor d such that sigma(d)*d is equal to k.at n=14A327599
• Numbers k such that gcd(k^2, 2^(k-1) - 1) > k.at n=3A331021
• Numbers k such that k divides A341038(k).at n=9A341039
• Triangular array read by rows: T(n,k) is the number of n X n idempotent matrices over GF(3) having rank k, n>=0, 0<=k<=n.at n=29A378666
• Triangular array read by rows: T(n,k) is the number of n X n idempotent matrices over GF(3) having rank k, n>=0, 0<=k<=n.at n=34A378666
• Numbers k such that sigma(A253560(k)) / A253560(k) is equal to (sigma(k)+1) / k, where A253560(k) = k multiplied by its largest prime factor.at n=29A387406
• Numbers k for which A053585(sigma(k)) is equal to A053585(k) and that satisfy also Euler's condition for odd perfect numbers (A228058).at n=7A388276