42241

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has odd period and if the last term of the periodic part is deleted the two central terms are both 16.at n=24A031604
• Number of ways to partition n labeled elements into sets of sizes of at least 2 and order the sets.at n=9A032032
• a(1) = 2, a(n+1) is the largest squarefree number < 2*a(n).at n=16A076994
• a(n) = Sum_{k=0..floor(n/2)} C(n-k,k)*C(n-k,k+1)/(n-k) * a(k), with a(0)=1.at n=14A118928
• Triangular array read by rows: T(n,k) is the number of ordered set partitions of {1,2,...,n} with exactly k singletons, n>=0, 0<=k<=n.at n=45A187784
• G.f.: A(x) = Sum_{n>=0} x^n/(1 - 4^n*x)^n.at n=5A193199
• Number T(n,k) of endofunctions on [n] such that at least one preimage with cardinality >=k exists and a nonempty preimage of j implies that all i<=j have preimages with cardinality >=k; triangle T(n,k), n>=0, 0<=k<=n, read by rows.at n=47A245732
• Composites in base 10 that remain composite in exactly three bases b, 2 <= b <= 10, expansions interpreted as decimal numbers.at n=1A256355
• Pseudoprimes to base 5, written in base 5.at n=8A262102
• Pseudoprimes to base 6, written in base 6.at n=19A262103