27221

Appears in sequences

• a(n) = (6*n+1)*(6*n+5).at n=27A001513
• Products of 2 successive primes.at n=37A006094
• a(n) is the smallest composite number c such that A002110(n) + c is prime.at n=36A038771
• a(n) = (4*n+3)*(4*n+7).at n=40A085027
• Indices of primes in the sequence defined by A(0) = 27, A(n) = 10*A(n-1) - 53 for n > 0.at n=5A101954
• Integer part of n#/(p-5)#, where p=preceding prime to n.at n=36A102791
• Integer part of n#/(p-7)#, where p=preceding prime to n.at n=35A102792
• Products of two successive primes that can be partitioned in sum of three distinct primes which contain the prime divisors.at n=11A109068
• Product of the n-th cousin prime pair.at n=12A143206
• a(n) = (8*n+3)*(8*n+7).at n=20A146301
• a(n) = 100*n^2 + 100*n + 21.at n=16A152161
• Number of partitions of n*(n+1)/2 with at most four parts that can be obtained from grouping (with parentheses) a permutation of the sum 1+2+...+n.at n=17A160438
• Number of binary strings of length n with no substrings equal to 0001, 1010, or 1100.at n=24A164487
• Numbers k such that exactly one d, 2 <= d <= k/2, exists which divides binomial(k-d-1, d-1) and is not coprime to k.at n=21A178071
• Fundamental discriminants of real quadratic number fields with class number 9.at n=32A218159
• Increasing a(n)is the smallest number of the form p^a*q^b, where a,b are positive integers and p < q are odd primes such that max( p^a, q^b)/min( p^a, q^b) <= 1 + 2/prime(n).at n=20A229108
• a(n) = prime(n)^2 - 4*prime(n).at n=36A245034
• Semiprimes whose prime factors are of equal binary length and which differ from each other in one bit position only.at n=26A261073
• Semiprimes whose prime factors differ from each other in one bit position only.at n=57A261077
• Semiprimes p*q for which p and q are successive primes and their binary representations differ from each other in one bit position only.at n=12A261080