18961

Appears in sequences

• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 78 ones.at n=23A031846
• Gaps of 7 in sequence A038593 (upper terms).at n=39A038654
• Logarithmic derivative of A112938 such that a(n)=(1/4)*A112938(n+1) for n>0, where A112938 equals the INVERT transform (with offset) of quadruple factorials A008545.at n=4A112939
• Semiprimes in A003215.at n=33A113530
• Numbers k such that k divides 1 plus the sum of the first k primes.at n=15A128165
• a(n) = 12*n^2 + 18*n + 7.at n=39A154105
• Least number k >= 0 such that (n!+k)/n is prime.at n=66A245695
• Riordan array (f(x)^4, f(x)), where 1 + x*f^4(x)/(1 - x*f(x)) = f(x).at n=22A263918
• Expansion of sqrt( cosh(x) / cos(x) ) = Sum_{n>=0} a(n) * x^(2n) / (2n)!.at n=5A273378
• Twice partitioned numbers where the first partition is constant and the latter partitions are strict.at n=36A279788
• a(n) = binomial(2*n,n) - ceiling(4^n/(2*sqrt(n))).at n=9A282710
• Triangle read by rows: T(n,k) is the number of rooted ordered trees with node weights summing to n, where the root has weight 0, all internal nodes have weight 1, and leaf nodes have weights in {1,...,k}.at n=51A384685