19042

Appears in sequences

• a(n) = prime(n)*prime(n-1) - 1.at n=33A023515
• Even semiprimes of the form prime(n)*prime(n+1) - 1.at n=6A103533
• Product of twin primes minus 1.at n=10A120875
• Triangle read by rows: T(n,k) = number of n-element unlabeled connected N-free posets of height k (1 <= k <= n).at n=49A202178
• Triangle read by rows: T(n,k) = number of n-element unlabeled connected N-free posets of height k (2 <= k <= n).at n=39A202179
• Number of (n+1) X 4 binary arrays with consecutive windows of two bits considered as a binary number nondecreasing in every row and column.at n=17A202330
• (1/2)*A206803.at n=35A206804
• a(n) = smallest index m such that smallest prime factor of m-th triangular number is prime(n).at n=32A226442
• Number of unlabeled rooted trees with n nodes such that the minimal outdegree of inner nodes equals 9.at n=50A244463
• Positive integers m such that none of the four consecutive numbers m, m+1, m+2, m+3 can be written as p^2 + q with p and q both prime.at n=11A258661
• Number of (1+1) X (n+1) arrays of permutations of 0..n*2+1 with each element having directed index change 0,1 0,-2 1,0 or -1,0.at n=15A264300
• Semiprimes which are the product of a twin prime pair minus one.at n=6A269663
• a(n) is the least k such that exactly n consecutive integers starting from k belong to A124665.at n=4A356272