23868

Appears in sequences

• Number of unrooted triangulations with reflection symmetry of a disk with one internal node and n+3 nodes on the boundary.at n=17A005508
• a(n) = 18*(n - 2)*(2*n - 5).at n=26A060787
• Expansion of (1+x^2*C^2)*C^2, where C = (1-(1-4*x)^(1/2))/(2*x) is g.f. for Catalan numbers, A000108.at n=9A071721
• a(n) = A000094(n+4) - A006918(n).at n=34A084835
• Sixth column of (1,5)-Pascal triangle A096940.at n=14A096943
• Inverse of Riordan array (1/(1-x)^2,x(1-x)/(1+x)), A104698.at n=36A110271
• Row sums of triangle A115237.at n=31A115238
• Location of record values in A080577; also partial sums of A006128 plus 1.at n=21A124920
• 3-comma numbers: n occurs in the sequence S[k+1]=S[k]+10*last_digit(S[k-1])+first_digit(S[k]) for three different splittings n=concat(S[0],S[1]).at n=28A166513
• Number of distinct values taken by 5th derivative of x^x^...^x (with n x's and parentheses inserted in all possible ways) at x=1.at n=23A199296
• Number of (n+2)X(1+2) 0..3 arrays with every 3X3 subblock row and column sum unequal to 4 or 5 and every diagonal and antidiagonal sum equal to 4 or 5.at n=6A251898
• Number of (n+2)X(7+2) 0..3 arrays with every 3X3 subblock row and column sum unequal to 4 or 5 and every diagonal and antidiagonal sum equal to 4 or 5.at n=0A251904
• T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row and column sum unequal to 4 or 5 and every diagonal and antidiagonal sum equal to 4 or 5.at n=21A251905
• T(n,k)=Number of (n+2)X(k+2) 0..3 arrays with every 3X3 subblock row and column sum unequal to 4 or 5 and every diagonal and antidiagonal sum equal to 4 or 5.at n=27A251905
• a(n) = sigma(n)*pi(n^2), where sigma(n) is the sum of all (positive) divisors of n, and pi(x) is the number of primes not exceeding x.at n=44A263325
• Those primitive elements of A337386 that have exactly one primitive nondeficient divisor (A006039).at n=7A341604
• Number of conjugacy classes in the group GL(4,Z_n).at n=11A364770
• a(n) = Sum_{i+j+k+m=n, i,j,k,m >= 1} tau(i) * tau(j) * tau(k) * tau(m).at n=18A375002
• Triangle read by rows: T(n,k) is the number of unlabeled simple connected graphs with n vertices and treedepth k.at n=42A387431
• a(n) = Sum_{k=0..floor(n/3)} binomial(n+k-1,k) * binomial(k,n-3*k).at n=15A389290