20806

Appears in sequences

• Denominators of continued fraction convergents to sqrt(650).at n=5A042249
• a(n) = 2*prime(n)*prime(n+1).at n=25A069486
• Numbers n such that sum of distinct primes dividing n is divisible by the largest prime dividing n. Also n is neither a prime, nor a true power of prime and n is squarefree. Squarefree solutions of A071140.at n=24A071141
• Numbers of the form 2*p*q where (p,q) is a twin prime pair.at n=8A071142
• Squarefree numbers k such that the largest prime factor of k is equal to the sum of the other prime factors of k.at n=23A071312
• Nonsquares with A072594(n) = 0.at n=37A072596
• Numbers k such that if P = 10*k^2+1, then P, P+6, P+12 and P+18 are all primes.at n=42A092446
• Numbers k = p*q*r (p, q, r prime) congruent to 0 mod p+q+r.at n=26A160394
• Triangle T(n,k), read by rows, given by (1, 2, -2, 0, 0, 0, 0, 0, 0, 0, ...) DELTA (1, 2, -1, 0, 0, 0, 0, 0, 0, 0, ...) where DELTA is the operator defined in A084938.at n=40A182412
• Squarefree numbers which yield zero when their prime factors are xored together.at n=12A235488
• Numbers k such that (13*10^k + 311)/9 is prime.at n=17A295031
• Number of 2 X n 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 2 neighboring 1s.at n=15A297432
• Number of even parts in the partitions of n into 7 parts.at n=47A309625
• a(n) is the largest integer x such that x/sopf(x) = prime(n) where sopf(x) is the sum of distinct prime factors of x and prime(n) is the n-th prime.at n=25A336493
• a(1) = 12; for n >= 2, a(n) = least positive integer of the form prime(m)*prime(n-m)*prime(n) with m >= 1.at n=26A364434