20847

Appears in sequences

• a(n+1) = a(n)-th composite number, with a(0) = 1.at n=39A006508
• Convolution of natural numbers >= 2 and Lucas numbers.at n=15A023549
• Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 96.at n=28A031594
• a(0) = a(1) = 1. a(n) = Sum_{p|n} a(n-p), where the sum is over all distinct primes p that divide n.at n=62A134192
• Number of length 4+3 0..n arrays with some disjoint pairs in every consecutive four terms having the same sum.at n=9A247536
• Indices of primes in the 10th-order Fibonacci number sequence, A127194.at n=35A257073
• Triangle T(n,m) by rows: The number of tatami tilings of a 2 X n grid with dimers and 2*m monomers.at n=57A272471
• Numbers k such that both Sum_{i=1..k} i*prime(i) and Sum_{i=1..k} (k+1-i)*prime(i) are prime.at n=33A356178