19909

Appears in sequences

• Centered cube numbers: n^3 + (n+1)^3.at n=21A005898
• Pseudoprimes to base 21.at n=36A020149
• Pseudoprimes to base 33.at n=42A020161
• Strong pseudoprimes to base 21.at n=10A020247
• Strong pseudoprimes to base 22.at n=12A020248
• Strong pseudoprimes to base 51.at n=15A020277
• a(n) = A050443(n-th prime)/(n-th prime).at n=19A052338
• Nonprimes k such that k divides 3^(k-1) - 2^(k-1).at n=36A073631
• Numbers n such that the sum of the proper divisors of n and n+1 equals either n or n+1.at n=20A130776
• a(1)=1, a(n)=a(n-1)+n^3 if n odd, a(n)=a(n-1)+ n^0 if n is even.at n=18A140152
• A general recursion triangle with third part a power triangle:m=4; Power triangle: f(n,k,m)=If[n*k*(n - k) == 0, 1, n^m - (k^m + (n - k)^m)]; Recursion: A(n,k,m)=(m*(n - k) + 1)*A(n - 1, k - 1, m) + (m*k + 1)*A(n - 1, k, m) + m*f(n, k, m)*A(n - 2, k - 1, m).at n=16A157631
• A general recursion triangle with third part a power triangle:m=4; Power triangle: f(n,k,m)=If[n*k*(n - k) == 0, 1, n^m - (k^m + (n - k)^m)]; Recursion: A(n,k,m)=(m*(n - k) + 1)*A(n - 1, k - 1, m) + (m*k + 1)*A(n - 1, k, m) + m*f(n, k, m)*A(n - 2, k - 1, m).at n=19A157631
• Totally multiplicative sequence with a(p) = a(p-1) + 9 for prime p.at n=28A166706
• Semiprime centered cube numbers: m^3 + (m+1)^3.at n=9A180082
• Number of nX6 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 1 0 and 1 0 1 vertically.at n=3A207517
• T(n,k)=Number of nXk 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 1 0 and 1 0 1 vertically.at n=39A207519
• Number of 4Xn 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 1 0 and 1 0 1 vertically.at n=5A207520
• a(n) = n*prime(prime(n)) - prime(n)^2.at n=49A230098
• Row sums of the triangular array A246694.at n=42A246695
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 838", based on the 5-celled von Neumann neighborhood.at n=44A273681