21365

Appears in sequences

• a(n) = floor( n*(n-1)*(n-2)*(n-3)/23 ).at n=28A011933
• Discriminants of real quadratic fields with class number 2 and related continued fraction period length of 21.at n=23A051986
• Number of length n+5 0..1 arrays with at most one downstep in every 5 consecutive neighbor pairs.at n=12A255989
• Numbers n such that 8*9^n - 1 is prime.at n=14A268356
• G.f.: Sum_{n=-oo..+oo} n * x^n * (1 - x^n)^n.at n=70A291937
• G.f. A(x) satisfies: 1 = Sum_{n>=0} ( (1+x)^(n^2) - A(x)^n )^n.at n=4A300152
• Number of integer partitions of n whose run-sums are not weakly increasing.at n=37A357865
• Number of integer partitions of n whose rounded mean is > 1. Partitions with mean >= 3/2.at n=37A364059