87448

Appears in sequences

• Numbers k such that 3*10^k + 5*R_k - 4 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=14A102971
• Number of Fermat pseudoprimes to base 7 less than 10^n.at n=11A114249
• a(1) = a(2) = 1, a(n) = a(n-1) + A007947(a(n-2)) for n >= 3, i.e., a(n) = a(n-1) plus the largest squarefree divisor of a(n-2).at n=29A121367
• G.f. satisfies: A(x) = A(x^2)^2 + x*A(x^2)^4.at n=25A174513
• Number of (n+1) X 3 0..3 arrays with the number of clockwise edge increases in every 2 X 2 subblock unequal to the number of counterclockwise edge increases.at n=2A206015
• Number of (n+1) X 4 0..3 arrays with the number of clockwise edge increases in every 2 X 2 subblock unequal to the number of counterclockwise edge increases.at n=1A206016
• T(n,k) = number of (n+1) X (k+1) 0..3 arrays with the number of clockwise edge increases in every 2 X 2 subblock unequal to the number of counterclockwise edge increases.at n=7A206021
• T(n,k) = number of (n+1) X (k+1) 0..3 arrays with the number of clockwise edge increases in every 2 X 2 subblock unequal to the number of counterclockwise edge increases.at n=8A206021
• a(0)=1, a(n) = least k > a(n-1) such that k*a(n-1) is a triangular number.at n=28A213005
• First row of spectral array W(gamma^2+1).at n=16A250254
• Number of (n+2)X(1+2) 0..3 arrays with every 3X3 subblock row and diagonal sum equal to 2 3 4 6 or 7 and every 3X3 column and antidiagonal sum not equal to 2 3 4 6 or 7.at n=14A252400