2097151

Appears in sequences

• a(n) = 2^n - 1. (Sometimes called Mersenne numbers, although that name is usually reserved for A001348.)at n=21A000225
• Maximum m such that there are no two adjacent elements belonging to the same n-th power residue class modulo some prime p in the sequence 1,2,...,m (equivalently, there is no n-th power residue modulo p in the sequence 1/2,2/3,...,(m-1)/m).at n=19A000236
• Divisors of 2^21 - 1.at n=11A003530
• Number of nonzero coefficients of order n in Baker-Campbell-Hausdorff expansion.at n=23A005489
• If n mod 4 = 0 then 2^(n-1)+1 elif n mod 4 = 2 then 2^(n-1)-1 else 2^(n-1).at n=21A007679
• Stirling numbers of second kind S2(22,n).at n=1A011571
• Jacobsthal-Lucas numbers.at n=21A014551
• Numbers k that divide 8^k - 1.at n=21A014949
• Nexus numbers (n+1)^21 - n^21.at n=1A022537
• a(n) = 8^n - 1.at n=7A024088
• a(n) = (n+1)^n - 1.at n=7A037205
• Maximum cycle length in differentiation digraph for n-bit binary sequences.at n=48A038553
• Number of 2n-bead balanced binary necklaces of fundamental period 2n which are equivalent to their reverse, complement and reversed complement.at n=43A045683
• a(n) = period of x^n + x + 1 over GF(2), i.e., the smallest integer m>0 such that x^n + x + 1 divides x^m + 1 over GF(2).at n=30A046932
• a(n) = period of x^n + x + 1 over GF(2), i.e., the smallest integer m>0 such that x^n + x + 1 divides x^m + 1 over GF(2).at n=23A046932
• Number of moves needed to solve an (n+1)-ring baguenaudier if two simultaneous moves of the two end rings are counted as one.at n=21A051049
• Expansion of 1/((1 - x)*(1 - 2*x^2)).at n=40A052551
• Expansion of 1/((1 - x)*(1 - 2*x^2)).at n=41A052551
• a(2n) = 2*2^n - 1, a(2n+1) = 3*2^n - 1.at n=40A052955
• Difference between 2^n and largest square strictly less than 2^n.at n=40A056007