27229

Appears in sequences

• Base-9 palindromes that start with 4.at n=32A043031
• Average of squares of successive primes: a(n) = (prime(n+1)^2 + prime(n)^2)/2, with n >= 2.at n=36A075892
• Numbers k such that phi(k) = phi(k+1) + phi(k+2).at n=3A197112
• Beach-Williams Pell numbers of type k^2 + 4.at n=8A212083
• Numbers n where tau(n) and n-tau(n) are perfect squares, with tau(n) the number of divisors of n (A000005).at n=42A245197
• Number of nX4 0..1 arrays with no element equal to more than three of its king-move neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.at n=4A281161
• Number of n X 5 0..1 arrays with no element equal to more than three of its king-move neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.at n=3A281162
• T(n,k)=Number of nXk 0..1 arrays with no element equal to more than three of its king-move neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.at n=31A281165
• T(n,k)=Number of nXk 0..1 arrays with no element equal to more than three of its king-move neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.at n=32A281165
• Number of intersection points formed by drawing the line segments connecting any two lattice points of an n X m convex lattice polygon written as triangle T(n,m), n >= 1, 1 <= m <= n.at n=25A288180
• Numbers k such that k!6 - 36 is prime, where k!6 is the sextuple factorial number (A085158).at n=25A289700
• Sequence a(n) = 3*A002559(n) - 2 determining the principal reduced indefinite binary quadratic form [1, a(n), -a(n)] for Markoff triples.at n=20A324250
• Semiprimes of the form k^2 + 4.at n=36A360741