21823

Appears in sequences

• Numbers k such that the period of the continued fraction for sqrt(k) contains exactly 35 ones.at n=5A031803
• Numerators of continued fraction convergents to sqrt(653).at n=6A042254
• n-th 4k+1 prime times (n+1)st 4k+3 prime.at n=16A048628
• Numbers k such that 4*10^k + 7*R_k is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=15A056708
• a(n) = prime(n)*prime(n+3).at n=33A090090
• Number of compositions a(1),...,a(k) of n, for some k, such that a(i+1) <= a(i) + 1 for 1 <= i < k and a(1) <= a(k) + 1.at n=18A168445
• a(n) = 2*n*(n+1)*(n+2)/3 + (-1)^n.at n=31A179783
• Number of permutations that have a fixed point and contain 123.at n=10A193364
• Numbers n for which A222085(n)=A222085(n+1).at n=22A222088
• S_9 sequence in partition of integers > 1 described in A240521.at n=40A240536
• Triangle read by rows: T(n,k) is the coefficient A_k in the transformation Sum_{k=0..n} x^k = Sum_{k=0..n} A_k*(x-3*(-1)^k)^k.at n=16A249269
• Semiprimes whose prime factors are of equal binary length and which differ from each other in exactly three bit positions.at n=38A261075
• Sequence of pairwise relatively prime numbers of class P_7 (see comment in A275246).at n=17A275252
• a(n) is the maximal permanent of an n X n symmetric matrix using all the integers from 0 to n*(n + 1)/2 - 1.at n=4A358809