2260992

Appears in sequences

• Theta series of laminated lattice LAMBDA_25 with minimal norm 4.at n=7A024211
• a(n)=(-1)^(n+1)*det(M(n)) where M(n) is the n X n matrix M(i,j)=min(abs(i-j),i).at n=20A080692
• Numbers of isomers of unbranched a-4-catapolypentagons - see Brunvoll reference for precise definition.at n=15A121135
• a(1)= 2. For n > 1, a(n) is the least number k such that k, k - a(n-1) and k + a(n-1) all have n prime divisors counted by multiplicity.at n=16A365852
• a(n) is the least number with n prime factors (counted with multiplicity) that is the concatenation of two primes.at n=16A374669