268435455

Appears in sequences

• a(n) = 2^n - 1. (Sometimes called Mersenne numbers, although that name is usually reserved for A001348.)at n=28A000225
• Number of 2n-bead balanced binary necklaces of fundamental period 2n, equivalent to reversed complement; also Dirichlet convolution of b_n=2^(n-1) with mu(n); also number of components of Mandelbrot set corresponding to Julia sets with an attractive n-cycle.at n=28A000740
• Generalized Euler phi function (for p=2).at n=28A003473
• Stirling numbers of second kind S2(29,n).at n=1A011578
• Number of Barlow packings with group P63/mmc(S) that repeat after 4n layers.at n=28A011946
• a(n) = 4^n - 1.at n=14A024036
• a(n) = Sum_{1<=k<=n, gcd(k,n)=1} 2^(k-1).at n=28A054432
• Number of primitive (aperiodic) word structures of length n which contain exactly two different symbols.at n=28A056278
• Table T(n,k) = T(n - 1,k) + T(n,k - 1) + T(n - 1,k)*T(n,k - 1) starting with T(0,0)=1, read by antidiagonals.at n=42A059328
• Table T(n,k) = T(n - 1,k) + T(n,k - 1) + T(n - 1,k)*T(n,k - 1) starting with T(0,0)=1, read by antidiagonals.at n=38A059328
• a(n) = 2^n + (-1)^(n+1).at n=28A062510
• Squarefree part of 2^n-1 : the smallest number such that a(n)*(2^n-1) is a square.at n=27A069112
• Expansion of (1-x)^(-1)/(1+x-2*x^2-2*x^3).at n=54A077896
• Number of irreducible indecomposable permutations of degree n.at n=29A078485
• Jacobsthal gap sequence.at n=28A080924
• Number of invertible circulant (0,1) matrices over the reals that have even determinant.at n=28A086479
• Smallest k such that k^4 - 1 is divisible by an n-th power, k > 1.at n=29A088041
• Smallest composite number with exactly n 1's in binary representation.at n=27A089226
• Start with the sequence [1, 1/2, 1/3, ..., 1/n]; form new sequence of n-1 terms by taking averages of successive terms; repeat until reach a single number F(n); a(n) = numerator of F(n).at n=27A090633
• A062402(x)=sigma(phi[x]) function is iterated; initial value=2^n; a(n)=smallest term of trajectory.at n=27A097002