-1806

Appears in sequences

• Consider the mapping f(a/b) = (a - b)/(ab). Taking a = 2 and b = 1 to start with and carrying out this mapping repeatedly on each new (reduced) rational number gives the following sequence 2/1,1/2,-1/2,-3/-2,-1/6,... Sequence contains the denominators.at n=9A081478
• Expansion of (1-x+sqrt(1-6x+x^2))/2 in powers of x.at n=7A085403
• Expansion of (1 + x + sqrt(1 - 6*x + x^2))/2 in powers of x.at n=7A086456
• Inverse of the Delannoy triangle.at n=28A103136
• First column of inverse of Delannoy triangle.at n=7A103137
• Riordan array ((1-x+sqrt(1+6*x+x^2))/2, (sqrt(1+6*x+x^2)-x-1)/2).at n=37A112477
• Riordan array ((1-x+sqrt(1-6x+x^2))/2, (1+x-sqrt(1-6x+x^2))/4).at n=28A117354
• Triangle, read by rows of coefficients of x^n*y^k for k=0..n(n-1)/2 for n>=0, defined by e.g.f.: A(x,y) = 1 + Series_Reversion( Integral A(-x*y,y) dx ), with leading zeros in each row suppressed.at n=34A144006
• A symmetrical triangle of polynomial coefficients based on the Hermite polynomials with leading coefficient adjusted to one: p(x,n)=HermiteH[n,x]-HermiteH[0,x]+x^n*(HermiteH[n,1/x]-HermiteH[0,1/x]).at n=29A176064
• A symmetrical triangle of polynomial coefficients based on the Hermite polynomials with leading coefficient adjusted to one: p(x,n)=HermiteH[n,x]-HermiteH[0,x]+x^n*(HermiteH[n,1/x]-HermiteH[0,1/x]).at n=34A176064
• Array: row n shows the coefficients of the characteristic polynomial of the n-th principal submatrix of {max(i,j)} (A051125).at n=40A203989
• Array: row n shows the coefficients of the characteristic polynomial of the n-th principal submatrix of max{2i+j-2,2j+i-2} (A204004).at n=41A204005
• Coefficients of mock modular form H_1^(2) of type 2A, divided by 2.at n=19A256059
• Expansion of (1 - x)*Sum_{k>=1} k*phi(k)*x^k/(1 - x^k), where phi() is the Euler totient function (A000010).at n=59A292302
• Dirichlet inverse of A341529, where A341529(n) = sigma(n) * A003961(n), and A003961 is fully multiplicative with a(prime(i)) = prime(i+1).at n=40A378229