18139

Appears in sequences

• Numbers k such that h(k) = h(k-1) + h(k-2), where h(k) = A006577(k) + 1 is the length of the sequence {k, f(k), f(f(k)), ...., 1} in the Collatz (or 3x + 1) problem. (The earliest "1" is meant.)at n=29A078418
• Numbers n such that h(n) = 2 h(n-1) where h(n) is the length of the sequence {n, f(n), f(f(n)), ...., 1} in the Collatz (or 3x + 1) problem. (The earliest "1" is meant.)at n=32A078419
• Semiperimeter of primitive Pythagorean triangles having legs that add up to a square, sorted on hypotenuse.at n=17A089549
• Integral quotients of products of consecutive composites divided by their sums: sums (divisors).at n=33A141091
• G.f.: 1/(1 - x/(1 - x^3/(1 - x^6/(1 - x^10/(1 - x^15/(1 - x^21/(1 -...- x^(n*(n+1)/2)/(1 -...))))))), a continued fraction.at n=27A206740
• Number of partitions of n such that the number of odd parts is a part and the number of even parts is not a part.at n=47A240578
• Partial sums of the number of active (ON, black) cells in n-th stage of growth of two-dimensional cellular automaton defined by "Rule 453", based on the 5-celled von Neumann neighborhood.at n=29A272275
• Partial sums of A175317 (Sum_{d|n} pod(d)).at n=20A280114
• Products of three distinct strong primes.at n=10A363782