20230

Appears in sequences

• Pentagonal pyramidal numbers: a(n) = n^2*(n+1)/2.at n=34A002411
• Even pentagonal pyramidal numbers.at n=25A015224
• Number of labeled 4-trees with n nodes.at n=7A036506
• Least k for which the integers Floor(k/(m*(m+1))) for m=1,2,...,n are distinct.at n=38A054061
• Multiples of 7 whose sum of digits is equal to 7.at n=32A063416
• Unitary weird numbers: unitary abundant (A034683) but not unitary pseudoperfect (A293188).at n=33A064114
• Nonsquares with A072594(n) = 0.at n=35A072596
• a(n)=floor{square((1*n^0+1*n^1+2*n^2+4*n^3)/(1*n^0+2*n^1+1*n^2))}.at n=36A086863
• a(n) = 4n^3 + 2n^2.at n=16A089207
• Triangle read by rows: T(n,r) = number of maximum r-uniform acyclic hypergraphs of order n and size n-r+1, 1 <= r <= n+1.at n=40A135021
• Triangle read by rows: T2[n,k] = Sum_{partitions of n with k parts p(n, k; m_1, m_2, m_3, ..., m_n)} c(n; m_1, m_2, ..., m_n) * x_1^m_1 * x_2^m_2 * ... x^n*m_n, where x_i = i-th prime.at n=24A145520
• Number of reduced words of length n in the Weyl group D_7.at n=19A162210
• Number of reduced words of length n in the Weyl group D_7.at n=23A162210
• a(n) = 17*n*(n+1).at n=34A173308
• [s(k)-s(j)]/6, where the pairs (k,j) are given by A205857 and A205858, and s(k) denotes the (k+1)-st Fibonacci number.at n=44A205860
• a(n) = F(n+8) - (1/6)*(n^4-2*n^3+26*n^2+47*n+132) where F(i) = Fibonacci numbers (A000045).at n=14A220889
• a(0)=0, a(1)=1, a(n) = min{3 a(k) + (3^(n-k)-1)/2, k=0..(n-1)} for n>=2.at n=34A259653
• Numbers n such that n!!! - 3^10 is prime, where n!3 = n!!! is a triple factorial number (A007661).at n=31A265201
• 38-gonal numbers: a(n) = n*(18*n-17).at n=34A282850
• Number of strings of n digits from 1...9 such that a signed summation of the digits exists making the sum = 0.at n=5A288550