18173

Appears in sequences

• Numbers k such that 8*R_k - 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=21A099422
• Counts 3-wild partitions. In general p-wild partitions of n are defined so that they are in bijection with geometric equivalence classes of degree n algebra extensions of the p-adic field Q_p. Here two algebra extensions are equivalent if they become isomorphic after tensoring with the maximal unramified extension of Q_p.at n=14A131140
• Positive numbers y such that y^2 is of the form x^2+(x+833)^2 with integer x.at n=34A156835
• a(n) = 12*n^2 - 2*n - 1.at n=39A185918
• a(n) = Sum_{i=0..n} digsum_3(i)^4, where digsum_3(i) = A053735(i).at n=57A231505
• G.f.: Sum_{n=-oo..+oo} Fibonacci(n+1) * x^n * (1-x^n)^n.at n=21A292498
• a(n) is the largest number that can be expressed as the sum of three positive triangular numbers in exactly n ways.at n=16A330811
• a(0) = a(1) = a(2) = 1, for n > 2, a(n) = a(n-1) + a(n-k) + k with k = 3.at n=27A362256