39900

Appears in sequences

• a(n) = n^2*(n^2 - 1)/4.at n=20A006011
• a(n) = (1/4)*floor(n/2)*floor((n-1)/2)*floor((n-2)/2)*floor((n-3)/2).at n=42A028723
• a(n) = (n-3)*A006918(n-2)/2 for n >= 2, with a(0) = a(1) = 0.at n=38A038376
• Partial sums of A007585.at n=17A051797
• Triangle read by rows: T(n,k) gives number of r-bicoverings of an n-set with k blocks, n >= 2, k = 3..n+floor(n/2).at n=22A060052
• Values of m such that N=(am+1)(bm+1)(cm+1) is a 3-Carmichael number (A087788), where a,b,c = 1,2,9.at n=34A064241
• Subdiagonal of array of n-gonal numbers A081422.at n=34A081423
• Second column (k=3) sequence of array A091746 ((6,2)-Stirling2) divided by 12.at n=2A091550
• Number of permutations p of (1,2,...,n) such that 1+k+p(k) is prime for all k=1,2,...,n.at n=13A103687
• Numbers k such that 1*k + 1, 3*k + 1, 9*k + 1, 27*k + 1 are all primes.at n=30A112041
• Numbers n that raised to the powers from 1 to k (with k>=1) are multiple of the sum of their digits (n raised to k+1 must not be a multiple). Case k=9.at n=31A135194
• A partition product of Stirling_2 type [parameter k = -3] with biggest-part statistic (triangle read by rows).at n=23A157399
• Numbers with prime factorization pqrs^2t^2.at n=18A189989
• G.f. satisfies: A(x) = (1 + x*A(x)^3) * (1 + x^2*A(x)^5).at n=7A211249
• Numbers with the property that in their factorization over distinct terms of A050376, the sums of prime and nonprime terms of A050376 are equal.at n=27A241270
• Exponential (2,3)-perfect numbers: numbers m such that esigma(esigma(m)) = 3m, where esigma(m) is the sum of exponential divisors of m (A051377).at n=35A328132
• Triangle read by rows: T(n,k) is the number of digraphs on n labeled nodes with k arcs and a global source and sink, n >= 1, k = 0..max(1,n-1)*(n-2)+1.at n=47A350791