31521

Appears in sequences

• Number of distinct primes in the numerator of the 2^n sums generated from the set 1, 1/2, 1/3, ..., 1/n.at n=19A075189
• Expansion of (7-14*x+6*x^2)/((1-x)*(2*x^2-4*x+1)); related to the binomial transform of Pell numbers A000129 (see formula and comment for A007070).at n=7A113859
• Expansion of -x*(5*x^4+5*x^3-7*x-4)/((x^2-x-1)*(x^3+x^2-1)).at n=26A134186
• Partial sums of A027444.at n=18A152457
• Composite squarefree numbers k such that p+1 divides k-1 for any prime p dividing k.at n=7A225711
• Number of balanced ternary words of length n.at n=31A260938
• a(n) = [x^n] (4*x^2 + x - 1)/(4*x^3 + 3*x^2 + 2*x - 1).at n=10A322939
• a(n) = Product_{d|n, d-1 is prime} (d-1)^(1+A286561(n,d-1)), where A286561(n,k) gives the k-valuation of n (for k > 1).at n=79A323155
• Odd composite integers m such that U(m)^2 == 1 (mod m) and V(m) == 7 (mod m), where U(m) and V(m) are the m-th generalized Lucas and Pell-Lucas numbers of parameters a=7 and b=-1, respectively.at n=36A337630
• Numbers which are the product of two S-primes (A057948) in exactly three ways.at n=32A343828
• Number of integer partitions of n such that the least and greatest parts are both even or both odd.at n=42A391225