19131876

Appears in sequences

• Expansion of (1+x)/(1-3*x).at n=15A003946
• a(1)=1, a(2)=2, a(n) = 4*3^(n-3) for n >= 3.at n=16A025579
• a(n) = Sum_{k=0..m} (k+1) * A026120(n, m-k), where m=0 for n=0,1; m=n for n >= 2.at n=15A027327
• Number of compositions of n into 2*j-1 kinds of j's for all j>=1.at n=16A052156
• Number of n-step walks (each step +-1 starting from 0) which are never more than 2 or less than -2.at n=30A068911
• a(2n+1) = 3^n, a(2n) = 4*3^(n-1) except for a(0) = 1.at n=30A074324
• a(1) = 4; a(n) = if n == 2 mod 3 then a(n-1)/2, if n == 0 mod 3 then a(n-1)*2, if n == 1 mod 3 then a(n-1)*3.at n=42A085689
• a(n) = n^2*9^n.at n=6A128788
• a(n) = (7*3^n - (-3)^n)/6.at n=15A133125
• Spiral tiling numbers.at n=27A137333
• Number of zig-zag paths from top to bottom of a rectangle of width 5 with n rows whose color is that of the top right corner.at n=29A153339
• a(n) = 3*a(n-2) for n > 2; a(1) = 4, a(2) = 3.at n=28A162766
• a(n) = 3*a(n-2) for n > 2; a(1) = 1; a(2) = 4.at n=29A166552
• Expansion of (1 - 2*x + 5*x^2) / (1 - 3*x)^2.at n=13A167682
• Number of reduced words of length n in Coxeter group on 4 generators S_i with relations (S_i)^2 = (S_i S_j)^16 = I.at n=15A167882
• Inverse binomial transform of A169609, or of A144437 preceded by 1.at n=30A168615
• Number of reduced words of length n in Coxeter group on 4 generators S_i with relations (S_i)^2 = (S_i S_j)^17 = I.at n=15A168681
• Number of reduced words of length n in Coxeter group on 4 generators S_i with relations (S_i)^2 = (S_i S_j)^18 = I.at n=15A168729
• Number of reduced words of length n in Coxeter group on 4 generators S_i with relations (S_i)^2 = (S_i S_j)^19 = I.at n=15A168777
• Number of reduced words of length n in Coxeter group on 4 generators S_i with relations (S_i)^2 = (S_i S_j)^20 = I.at n=15A168825