21693

Appears in sequences

• a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ... + a(n-3)*a(3) for n >= 4, with initial terms 1, 3, 1, 1.at n=13A025255
• Numbers m such that 2^m reversed is prime.at n=30A057708
• Smallest number which requires n iterations to reach a prime when iterating x + sum of squares of digits of x.at n=51A094658
• a(n) = Re(b(n)) where b(n)=(1+i)*b(n-1)+b(n-2), with b(1)=0, b(2)=1.at n=25A143056
• Number of (n+1) X (1+1) 0..2 arrays with 2 X 2 edge jumps all no more than +1 in one of the clockwise or counterclockwise directions or both.at n=3A235216
• Number of (n+1)X(4+1) 0..2 arrays with 2X2 edge jumps all no more than +1 in one of the clockwise or counterclockwise directions or both.at n=0A235219
• T(n,k)=Number of (n+1)X(k+1) 0..2 arrays with 2X2 edge jumps all no more than +1 in one of the clockwise or counterclockwise directions or both.at n=6A235223
• T(n,k)=Number of (n+1)X(k+1) 0..2 arrays with 2X2 edge jumps all no more than +1 in one of the clockwise or counterclockwise directions or both.at n=9A235223
• Number of partitions p of n such that the number of parts is a part and max(p) - min(p) is not a part.at n=50A241384
• Triangle read by rows: T(n, k) = C(n, k)*C(2*k, k)/(k+1) - sum(j = 0..k, (-1)^j*(1-j)^n*C(k, j)/k!), 0<=k<=n.at n=61A247493
• Number of (unordered) plane trees with n leaves, such that for every node the number of "children of children" has no common divisor > 1.at n=12A354076
• G.f. A(x) satisfies A(x) = 1 + x^3*(1+x)*A(x)^3.at n=20A376547