21509

Appears in sequences

• Numbers k such that the continued fraction for sqrt(k) has period 63.at n=26A020402
• Shifts left under transform T where Ta is (identity) DCONV a.at n=45A038046
• a(n) = 2^(n-1)*(5*n-8) + 5.at n=10A048498
• n-th 6k+1 prime times n-th 6k-1 prime.at n=16A048629
• Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 19.at n=12A051984
• Sum of a(n) terms of 1/k^(3/4) first exceeds n.at n=45A056179
• Number of irreducible representations of the symmetric group S_n that have even degree.at n=36A060368
• Smallest odd number k>1 such that k*2^A000043(n)+1 is a prime number.at n=26A253027
• Semiprimes whose prime factors are of equal binary length and which differ from each other in exactly two bit positions.at n=44A261074
• The number of partitions of n which represent Chomp positions with Sprague-Grundy value 8.at n=58A284781
• Decimal representation of the diagonal from the corner to the origin of the n-th stage of growth of the two-dimensional cellular automaton defined by "Rule 485", based on the 5-celled von Neumann neighborhood.at n=32A288594
• Counterexamples to a conjecture of Ramanujan about congruences related to the partition function.at n=35A340757
• Number of ways that n can be expressed as a sum of consecutive integers from 0 up to at most n, where any of the terms in the sum can be negated, and the partial sum from 0 is always between 0 and n inclusive.at n=58A364721