21234

Appears in sequences

• 5th forward differences of factorial numbers A000142.at n=3A001689
• Squares written in base 5.at n=38A001740
• Triangular array formed from successive differences of factorial numbers.at n=41A047920
• Triangle T[n,m]: T[n,-1] = 0; T[0,0] = 0; T[n,0] = n*n!; T[n,m] = T[n,m-1] - T[n-1,m-1].at n=32A061312
• Euler's difference table: triangle read by rows, formed by starting with factorial numbers (A000142) and repeatedly taking differences. T(n,n) = n!, T(n,k) = T(n,k+1) - T(n-1,k).at n=39A068106
• Table T(n,k) giving number of ways of obtaining exactly one correct answer on an (n,k)-matching problem (1 <= k <= n).at n=41A076732
• Difference triangle of factorial numbers read by upward diagonals.at n=30A116853
• First differences of the rows in the triangle of A116853, starting with 0.at n=39A116854
• Triangle of rank k of permutations of {1,2,...,n}.at n=50A134830
• Append three digits, each increasing by one modulo 10 from the last digit of the nonnegative integers. 0 -> 123, 1 -> 1234 2 -> 2345, ... , 9 -> 9012, 10 -> 10123, etc.at n=21A167231
• Number of 4 X n binary arrays without the pattern 0 1 diagonally, vertically, antidiagonally or horizontally.at n=27A188555
• a(n) = Sum_{i+j+k=n, i,j,k >= 1} tau(i)*tau(j)*tau(k), where tau() = A000005().at n=36A191829
• Triangle read by rows: T(n, k) = Sum_{t=k..n-3} (-1)^(t-k)*(n-t)!*binomial(t,k)*binomial(n-3,t).at n=15A264028
• Fourth column of Euler's difference table in A068106. It is 6 times the sequence A000261.at n=7A277609
• Chromatic invariant of the n-cocktail party graph.at n=4A295166
• a(n) is the smallest b >= 2 such that b^(6*2^n) - b^(3*2^n) + 1 is prime.at n=11A298206
• Triangle read by rows: T(n, k) = (Sum_{i=0..n-k} (-1)^i * binomial(n-k, i) * (n+2-i)!) * binomial(n, k) / ((k+1) * (k+2)) for 0 <= k <= n.at n=22A373050
• a(n) is the smallest integer k > 2*n such that Product_{i=1..n} (k - i) has no prime factor p in n < p < 2*n.at n=28A386620