20019

Appears in sequences

• Let c(k) denote the k-th composite number and p(k) the k-th prime number; then a(n) = Sum_{i=n*(n-1)/2+1 .. n*(n+1)/2} c(i) - Sum_{i=1..n} p(i).at n=32A024850
• Numbers whose trajectory under the Esucarys map ends at the fixed point 247.at n=26A129133
• Odd nonprimes n such that n+d+1 is prime for all divisors d of n.at n=35A187554
• Floor-Sqrt transform of Motzkin numbers (A001006).at n=22A192669
• Number T(n,k) of set partitions of [n] such that the maximal absolute difference between the least elements of consecutive blocks equals k; triangle T(n,k), n>=0, 0<=k<=max(n-1,0), read by rows.at n=50A287215
• Number of set partitions of [n] such that the maximal absolute difference between the least elements of consecutive blocks equals four.at n=6A322877
• a(n) is the minimum positive integer k such that the concatenation of k, a(n-1), a(n-2), ..., a(2), and a(1) is the lesser of a pair of twin primes (i.e., a term of A001359), with a(1) = 11.at n=29A350246