2086561

Appears in sequences

• a(n) = 2*a(n-1) + a(n-2) - a(n-3), with a(0) = a(1) = 0, a(2) = 1.at n=20A006054
• 3-wave sequence starting with 1, 1, 1.at n=37A038196
• Expansion of g.f.: 1/(1 - 2*x - x^2 + x^3).at n=18A106805
• Semiprimes in A006054.at n=3A122500
• Let i be in {1,2,3}, let r >= 0 be an integer and n=2*r+i-1. Then a(n)=a(2*r+i-1) gives the quantity of H_(7,1,0) tiles in a subdivided H_(7,i,r) tile after linear scaling by the factor x^r, where x=sqrt((2*cos(Pi/7))^2-1).at n=41A187068
• Let i be in {1,2,3}, let r >= 0 be an integer and n=2*r+i-1. Then a(n)=a(2*r+i-1) gives the quantity of H_(7,2,0) tiles in a subdivided H_(7,i,r) tile after linear scaling by the factor x^r, where x=sqrt((2*cos(Pi/7))^2-1).at n=40A187069
• Let i be in {1,2,3}, let r >= 0 be an integer and n=2*r+i-1. Then a(n)=a(2*r+i-1) gives the quantity of H_(7,3,0) tiles in a subdivided H_(7,i,r) tile after linear scaling by the factor x^r, where x=sqrt((2*cos(Pi/7))^2-1).at n=39A187070
• Maximal term of TRIP-Stern sequence of level n corresponding to permutation triple (e,13,e).at n=35A271485
• a(n) is the number of symmetrical linear hydrocarbon chains with n C-C bonds.at n=36A370377