20053

Appears in sequences

• Discriminants of real quadratic fields with class number 1 and related continued fraction period length of 24.at n=54A051965
• Triangle of number of rises in restricted growth strings (RGS) for the set partitions of n.at n=58A056858
• Number of binary reversal primes less than 10^n.at n=5A074831
• Numbers k such that k + sigma(k) + sigma(sigma(k)) is a square.at n=38A116014
• Sum of median parts of all partitions of n into an odd number of parts.at n=35A211373
• Consider a number n with m decimal digits. The sequence lists the numbers n having the suffix of length m-1 in the middle of the decimal expansion of prime(n).at n=42A242957
• Expansion of Product_{i>=2, j>=2} (1 + x^(i*j))^j.at n=34A326831
• a(n) = Sum_{1 <= i, j, k <= n} gcd(i,j,k).at n=24A344522
• Numbers k such that k, k+1, k+2, k+3 have 2, 3, 4, 5 prime factors respectively, counted with multiplicity.at n=23A363391
• Squarefree semiprimes k such that k+1 is the product of three distinct primes and k+2 is the product of four distinct primes.at n=21A376352