21080

Appears in sequences

• Coordination sequence for Cr3Si, Si position.at n=37A009927
• Number of partitions of n with equal number of parts congruent to each of 1 and 3 (mod 5).at n=51A035557
• Numbers n such that 279*2^n-1 is prime.at n=24A050898
• Numbers n such that 1n1, 3n3, 7n7 and 9n9 are all primes.at n=31A059677
• Largest term in periodic part of continued fraction expansion of square root of n-th repunit.at n=8A096487
• Coefficients of polynomials S(n,x) related to Springer numbers.at n=8A098432
• In the interior of a regular 2n-gon with all diagonals drawn, the number of points where exactly three diagonals intersect.at n=29A101363
• Inverse of Riordan array (1/(1-x), x/(1-x)^4), A109960.at n=40A109962
• Antidiagonal sums of table A125860.at n=7A125859
• The fourth row of the ED2 array A167560.at n=16A167561
• Smith numbers of order 3.at n=4A178213
• Iterates of f(x)=floor((3x-1)/2) from x=6.at n=21A183208
• For positive n with prime decomposition n = Product_{j=1..m} (p_j^k_j) define A_n = Sum_{j=1..m} (p_j*k_j) and B_n = Sum_{j=1..m} (p_j^k_j). This sequence gives those n for which A_n and B_n are both prime and B_n = A_n + 2 (i.e., form a twin prime pair).at n=38A185718
• Number of distinct (unordered) pairs of partitions of a 10-element set that have Rand distance n.at n=35A192103
• Antidiagonal sums of the convolution array A213849.at n=29A213850
• a(n) = n*(n + 11)*(n + 22)/6.at n=40A264445
• a(n) = n*(2*n+1)*binomial(n+2,n)/3.at n=15A289643
• Triangle T(n, k) read by rows: row n gives the coefficients of the numerator polynomials of the o.g.f. of the (n+1)-th diagonal of the Sheffer triangle A154537 (S2[2,1] generalized Stirling2), for n >= 0.at n=17A290315
• Expansion of Product_{k>=0} (1 + x^(4^k))^(4^(k+1)).at n=24A321355
• Number of non-isomorphic phylogenetic trees with n nodes.at n=22A330627