18103

Appears in sequences

• a(n) = 4*a(n-1) + 7*a(n-2).at n=7A015532
• Pseudoprimes to base 21.at n=32A020149
• Pseudoprimes to base 33.at n=41A020161
• Strong pseudoprimes to base 51.at n=14A020277
• a(n) = least semiprime with factors not previously used containing integers 2n and 2n+1 as substrings.at n=21A086887
• Number of walks within N^3 (the first octant of Z^3) starting at (0,0,0) and consisting of n steps taken from {(-1, -1, 0), (0, 1, -1), (1, 0, 1), (1, 1, 1)}.at n=8A150389
• Number of permutations of 1..n containing the relative rank sequence { 124563 } at any spacing.at n=3A159084
• Number of permutations of 1..n containing the relative rank sequence { 163452 } at any spacing.at n=3A159133
• Numbers of the form 6^j + 7^k, for j and k >= 0.at n=34A226819
• Composites c where at least one base b with 1 < b < c exists such that b^(c-1) == 1 (mod c^2), i.e., composites c that are base-b 'Wieferich pseudoprimes' for at least one b between 1 and c.at n=41A267288
• Row 4 of A328464: a(n) = A276156(16n - 8) / 30.at n=15A328467
• Numbers of the form h^i + k^j where h,i,j,k are distinct positive integers and max{h,i,j,k} - min{h,i,j,k} = 3.at n=34A391670