31081

Properties

Appears in sequences

• Smallest prime p such that the product of q/(q-1) over the primes from prime(n) to p is greater than 2.at n=38A001275
• Reflectable emirps.at n=26A007628
• Numbers k such that k, k+1, k+2 and k+3 are 1,2,3,4-almost primes.at n=27A113000
• Prime numbers p such that p +- ((p-1)/4) are primes.at n=30A137705
• Prime numbers p such that p +- ((p-1)/7) are primes.at n=16A137770
• Primes in A005891 = Centered pentagonal numbers: (5n^2 + 5n + 2)/2.at n=18A145838
• a(n) = 29 + 73*n + 37*n^2.at n=28A145980
• Greater of twin primes p such that 3*p-2 is also greater of twin primes.at n=13A177336
• Larger of emirp pairs whose digital sums are also emirps (A178091).at n=38A178093
• Cyclops emirps.at n=36A183057
• Primes p of the form 420k + 1 for some k.at n=30A217587
• Primes p of the form p = 1 + 840*k for some k.at n=18A217862
• G.f.: Sum_{n>=0} x^n * Sum_{k=0..n} binomial(n,k)^4 * x^k*(1-x)^(n-k).at n=8A218216
• Expansion of 1/(1 - x^3 - x^4 - x^5 - x^6 + x^9).at n=38A225484
• Number of compositions of 2n into parts with multiplicity <= n.at n=8A232605
• Number of compositions of n into parts with multiplicity not larger than 8.at n=16A243086
• T(n,k)=Number of nXk 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 1 neighboring 1.at n=58A297395
• Number of 4 X n 0..1 arrays with every 1 horizontally, diagonally or antidiagonally adjacent to 1 neighboring 1.at n=7A297397
• Number of integer partitions of n that reduce to 2, meaning their Heinz number maps to 2 under A304464.at n=39A319153
• Number of integer partitions of n with omicron 2.at n=40A325267