18977

Appears in sequences

• Total number of fixed points in free homeomorphically irreducible trees with n nodes.at n=19A037246
• Denominators of convergents to Pi by Farey fractions.at n=35A063673
• Non-palindromic n and its digit reversal have the same sum of prime factors (with repetition).at n=40A085607
• Decimal value of binary number whose n-th 1 is followed by L(n) 0's.at n=3A117085
• Number of permutations of 1..n with displacements restricted to {-4,-3,0,1,2}.at n=14A189581
• Fundamental discriminants d uniquely characterizing all complex biquadratic fields Q(sqrt(-3),sqrt(d)) which have 3-class group of type (3,3) and second 3-class group isomorphic to SmallGroup(729,95).at n=8A250239
• Non-palindromic composite numbers such that n' = [Rev(n)]', where n' is the arithmetic derivative of n.at n=12A259077
• a(n) = greatest k such that A155043(k+A262509(n)) < A155043(A262509(n)).at n=44A262909
• Number of active (ON, black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 406", based on the 5-celled von Neumann neighborhood.at n=7A271887
• Number of compositions of n with runs-resistance 2.at n=18A329745
• Numbers m such that A338038(m) = A338038(A004086(m)) where A004086(i) is i read backwards and A338038(i) is the sum of the primes and exponents in the prime factorization of i ignoring 1-exponents; palindromes and multiples of 10 are excluded.at n=35A338039
• Triangle read by rows: T(n,k) is the number of rooted ordered trees with node weights summing to n, where the root has weight 0, all internal nodes have weight 1, and leaf nodes have weights in {1,...,k}.at n=54A384685