81719

Appears in sequences

• Lucas-Carmichael numbers: squarefree composite numbers k such that p | k => p+1 | k+1.at n=23A006972
• a(n) = floor( binomial(n,8)/9).at n=24A011845
• a(n) = floor( binomial(n,9)/10 ).at n=23A011846
• Number of necklaces with 9 black beads and n-9 white beads.at n=16A032194
• Numbers of nonisomorphic systems of catafusenes (see Cyvin et al. (1994) for precise definition).at n=9A045906
• Indices of square numbers which are also 9-gonal.at n=7A048911
• T(2n+7,n), array T as in A051168; a count of Lyndon words.at n=9A050185
• a(n) = ceiling(binomial(n,9)/n).at n=24A053733
• Quotient: squarefree kernel of A002944(n) divided by that of A001405.at n=47A056611
• Quotient: squarefree kernel of A002944(n) divided by that of A001405.at n=48A056611
• Composite numbers k that divide Fibonacci(k+1).at n=28A069107
• a(n) = n*(n+1)*(2*n^2+1)/6.at n=22A071238
• Numbers k that divide Fibonacci(k+1) but do not divide Fibonacci(k) + 1.at n=24A094412
• Product of primes which do not exceed n and do not divide the swinging factorial n$ (A056040).at n=49A163644
• Numbers n such that n and n+-1 have 4 distinct prime factors.at n=20A168628
• Composite numbers k that divide both Fibonacci(k+1) and Fibonacci(2k+1)-1.at n=27A182504
• Numbers such that the sum of the squares of the largest and the smallest prime divisor equals the sum of the squares of the other distinct prime divisors.at n=1A199857
• Lucas-Carmichael numbers with 4 prime factors.at n=6A216926
• Leading diagonal of triangle in A222310.at n=23A222311
• Number of (n+2) X (7+2) 0..1 arrays with no 3 x 3 subblock diagonal sum 0 and no antidiagonal sum 3 and no row sum 1 and no column sum 1.at n=23A257446