81047

Properties

Appears in sequences

• Number of binary vectors of length n+1 beginning with 0 and containing just 1 singleton.at n=22A006367
• Crystal ball sequence for hexagonal close-packing.at n=28A007202
• Primes of the form Sum_{k=1..n} phi(prime(k)).at n=31A101302
• Primes p such that p + 2, 18*p^2 + 1, and 18*(p+2)^2 + 1 are all primes.at n=23A115272
• Prime quadruples: 3rd term.at n=33A136721
• Lesser of twin primes p1 such that p1*p2-4 and p1*p2-6 are twin prime numbers.at n=31A174957
• a(n+1) is the smallest prime > a(n) such that the digits of a(n) are all (with multiplicity) contained in the digits of a(n+1), with a(1)=7.at n=18A242907
• Prime numbersat n=7934