30691

Appears in sequences

• Number of 3 X 3 integer matrices with elements in the range [ -n,n ] which generate a group of order two under binary matrix multiplication.at n=10A054466
• Triangle read by rows: T(n,k) is the number of Schroeder paths of length 2n and having k up steps starting at even heights.at n=47A101919
• Triangle read by rows: T(n,k) is the number of Schroeder paths of length 2n and having k up steps starting at an odd height.at n=37A101920
• a(1) = 1; for n > 1, a(n) is the least k > a(n-1) such that a(n) + a(n-1) is square and a(n) - a(n-1) is prime.at n=27A108972
• Triangle read by rows: T(n,k) is number of ordered trees with n edges and having exactly k vertices all of whose children are leaves (1<=k<=floor(n/2) for n>=2).at n=27A114502
• Enneagonal numbers for which the product of the digits is also an enneagonal number.at n=31A117052
• Triangle read by rows: T(n,k) is the number of Grand Dyck paths of semilength n that have k double rises above the x-axis (n >= 1, k >= 0).at n=47A118964
• Triangle T(n,k), read by rows, defined by T(n,k)=3*T(n-1,k)-T(n-1,k-1)-T(n-2,k), T(0,0)=1, T(1,0)=2, T(1,1)=-1, T(n,k)=0 if k<0 or if k>n.at n=47A123971
• Binomial transform of [1, 30, 30, 30, ...].at n=10A139700
• Triangle read by rows: T(n,k) is the number of Dyck paths of semilength n having k peak plateaux (0<=k<=floor(n/2)). A peak plateau is a run of consecutive peaks that is preceded by an upstep and followed by a down step; a peak consists of an upstep followed by a downstep.at n=38A143952
• a(n) = IntegerPart(PolyGamma(n, 3)).at n=14A144169
• a(n) = n^3 + (1-n)^2.at n=31A168297
• Triangle read by rows: T(n,k) is the number of bargraphs of semiperimeter n having k peaks (n >= 2, k >= 1).at n=24A271940
• 9-gonal numbers that are semiprimes.at n=11A356424
• Numerators of the partial alternating sums of the reciprocals of the sum of divisors function (A000203).at n=9A357845
• Constant term in the expansion of (1 + x^4 + y^4 + 1/(x*y))^n.at n=12A361700
• a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} gcd(x_1, x_2, n)/gcd(x_1, x_2, x_3, n).at n=30A373061