20216

Appears in sequences

• Cubes written in base 7.at n=16A004637
• a(n) = 2*a(n-1) + a(n-2) - a(n-3) for n >= 3, starting with a(0) = 1, a(1) = 3, and a(2) = 6.at n=12A006356
• 3-wave sequence starting with 1, 1, 1.at n=26A038196
• Bottom line of 3-wave sequence A038196, also bisection of A006356.at n=6A038223
• Consider sequence of fractions A066657/A066658 produced by ratios of terms in A066720; let m = smallest integer such that all fractions 1/n, 2/n, ..., (n-1)/n have appeared when we reach A066720(m) = k; sequence gives values of k; set a(n) = -1 if some fraction i/n never appears.at n=13A066848
• Expansion of (1-x)/(1-2*x-x^2+x^3).at n=13A077998
• Number of odd composites 1 mod 4 less than 10^n.at n=4A093151
• Expansion of x*(1-x)/(1-2*x-x^2+x^3).at n=14A106803
• Triangle read by rows: numbers of isomers of unbranched a-4-catapolyheptagons.at n=48A120653
• Expansion of ( 1-x^3+x^4+x^5-x^8 ) / ( 1-2*x^3-x^6+x^9 ).at n=39A120771
• Expansion of ( 1-x^3+x^4+x^5-x^8 ) / ( 1-2*x^3-x^6+x^9 ).at n=44A120771
• Numbers of isomers of unbranched a-4-catapolyheptagons - see Brunvoll reference for precise definition.at n=6A121140
• First row sum of the matrix M^n, where M is the 3 X 3 matrix [[6, 5, 3], [5, 4, 2], [3, 2, 1]] (n>=0).at n=4A122187
• Number of species of connected separated Latin bi-trades of size n.at n=16A133165
• a(n) = 14*n^2.at n=38A144555
• Triangle T(n,k) = binomial(n, k)*(k! + (n-k)!), read by rows.at n=38A155162
• Triangle T(n,k) = binomial(n, k)*(k! + (n-k)!), read by rows.at n=42A155162
• 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=30A187068
• 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=28A187070
• Coefficient of x in the reduction by x^2 -> x+1 of the polynomial p(n,x) defined below in Comments.at n=8A192429