216821881

Appears in sequences

• Carmichael numbers of the form (6*k+1)*(12*k+1)*(18*k+1), where 6*k+1, 12*k+1 and 18*k+1 are all primes.at n=5A033502
• Carmichael numbers of the form C = (30n-p)*(60n-(2p+1))*(90n-(3p+2)), where n is a natural number and p, 2p+1, 3p+2 are all three prime numbers.at n=8A182087
• a(1) = 561; a(n+1) = smallest Fermat pseudoprime to all natural bases up to lpf(a(n)).at n=15A300629
• Carmichael numbers whose prime factors form an arithmetic progression.at n=12A300949
• Numbers of the form: (6*m + 1) * (12*m + 1) * Product_{i=1..k-2} (9 * 2^i * m + 1), where k >= 3, with the condition that each of the factors is prime and that m is divisible by 2^(k-4).at n=6A317126
• Carmichael numbers (A002997) that are not minimal in their family.at n=17A335584
• Records in A083876.at n=15A348258