26106

Appears in sequences

• Total height of all rooted trees on n labeled nodes.at n=5A001854
• a(n) = -6 + 2^(n+1)*(3 - 2*n + n^2).at n=8A036800
• Smallest triangular number whose final digits are A068125(n).at n=48A068126
• Triangular numbers with sum of digits = 15.at n=32A068130
• Triangular numbers whose sum of prime factors (with repetition) is also triangular.at n=21A076169
• a(n) = p(n)*(p(n)-1)/2 where p(n) = upper member of n-th pair of twin primes.at n=15A082669
• a(n) = smallest k where (10^k+1)=0 mod prime(n)^2, or 0 if no such k exists.at n=49A086981
• a(n) = 3*n*(6*n + 1).at n=38A144314
• Sum of tetrahedral numbers A000292(k), with k in the reduced residue system modulo n.at n=35A189918
• Index of the smallest Fibonacci number divisible by prime(n)^2.at n=49A264008
• Triangular numbers that are the product of four distinct primes.at n=32A333771
• Triangular numbers that are the sum of two distinct nonzero triangular numbers in exactly two ways.at n=13A350368
• Square array T(n,k), n >= 0, k >= 0, read by antidiagonals downwards, where T(n,k) = Sum_{j=0..n} k^j * j^k.at n=63A368486