129780

Appears in sequences

• Starting positions of strings of four 8's in the decimal expansion of Pi.at n=13A083638
• Triangle, read by rows, defined by T(n, k) = b(n, k) + b(n, n-k+1) - (b(n,1) + b(n,n)) + 1, where b(n, k) = (-1)^n*(n!/k!)^2 *binomial(n-1, k-1).at n=16A169658
• Triangle, read by rows, defined by T(n, k) = b(n, k) + b(n, n-k+1) - (b(n,1) + b(n,n)) + 1, where b(n, k) = (-1)^n*(n!/k!)^2 *binomial(n-1, k-1).at n=19A169658
• Triangle read by rows: T(n,k) is the number of permutations of [n] starting with 1, having no 3-sequences and having k successions (0 <= k <= floor(n/2)); a succession of a permutation p is a position i such that p(i +1) - p(i) = 1.at n=46A180186
• Smallest number k such that prime(n) is the n-th divisor of k.at n=25A221647
• Related to enumeration of sets of non-intersecting circles in the plane.at n=10A281346
• Triangle read by rows, a refinement of the central Stirling numbers of the first kind A187646, T(n, k) for n >= 0 and 0 <= k <= n.at n=16A293609
• a(n) = (1/2)*(n + 1)*(5*n^2 + 15*n + 6)*Pochhammer(n, 6) / 6!.at n=5A293612