28861

Appears in sequences

• a(n) = A050443(n-th prime)/(n-th prime).at n=20A052338
• Triangle of numbers of inequivalent Boolean functions of n variables with exactly k nonzero values (atoms) under action of complementing group.at n=42A054724
• q-factorial numbers 3!_q.at n=30A069778
• p(p^2-p+1) as p runs through the primes.at n=10A083558
• Number of Pythagorean quadruples mod n; i.e., number of solutions to w^2 + x^2 + y^2 = z^2 mod n.at n=30A096018
• Least number k such that lcm{1,2,...,k}/denominator of harmonic number H(k) = 2n-1.at n=15A112822
• a(0)=1, a(1)=1, a(n) = 13*a(n/2) for n=2,4,6,..., a(n) = 12*a((n-1)/2) + a((n+1)/2) for n=3,5,7,....at n=19A116524
• a(n) = n*(n^2 + 2*n - 1)/2.at n=37A127736
• Square array T(n, k) = Product_{j=1..n} ( Sum_{i=0..j-1} ((k+1)^2 - (k+1))^i ) with T(n, 0) = n!, read by antidiagonals.at n=39A156881
• Integers equal to sqrt(A169652(n)/900).at n=2A176349
• Numbers k such that sopfr(k + omega(k)) = sopfr(k), where sopfr(i) = A001414(i) and omega(i) = A001221(i).at n=26A187878
• Number of (n+3) X 9 binary arrays with every 4 X 4 subblock commuting with each horizontal and vertical neighbor 4 X 4 subblock.at n=12A188102
• Number of -3..3 arrays x(i) of n+1 elements i=1..n+1 with set{t,u,v in 0,1}((x[i+t]+x[j+u]+x[k+v])*(-1)^(t+u+v)) having one, three, four, five, six, seven or eight distinct values for every i,j,k<=n.at n=4A211765
• Number of distinct finite languages over 4-ary alphabet, whose minimum regular expression has ordinary length n.at n=6A211954
• The number of permutations of length n sortable by 3 prefix reversals (in the pancake sorting sense).at n=31A228398
• a(n) = Sum_{i=0..n} digsum_8(i)^4, where digsum_8(i) = A053829(i).at n=24A231683
• The number of P-positions in the game of Nim with up to 4 piles, allowing for piles of zero, such that the number of objects in each pile does not exceed n.at n=30A241522
• Number of ordered unlabeled rooted trees with n nodes such that the minimal outdegree of inner nodes equals 9.at n=29A244538
• Number of ways to write n as an ordered sum of 7 primes.at n=33A340963
• a(n) = m is the least m = b*c > a(n-1) such that (b+c)*n = m-1 where 1 < b <= c < m.at n=29A364171