31980

Appears in sequences

• a(n) = n*(n+1)*(n+2)/2.at n=39A027480
• Congruence classes of triangles which can be drawn using lattice points in n X n grid as vertices.at n=20A028419
• a(n) = n*(2*n-1)*(2*n+1).at n=20A035328
• Numbers n such that sopf(n) = sopf(n-1) - sopf(n-2), where sopf(x) = sum of the distinct prime factors of x.at n=10A076527
• Least common multiple of {d-1: d > 1 and d divides n}.at n=41A084190
• Number of perfect rulers with length n.at n=59A103300
• Elements of A065607 from primitive triples.at n=28A120693
• Minimum k>0 such that Sum_{i=1..n} Fibonacci(i)*k^(i-1) is prime.at n=37A121927
• a(n) = n*(n^2 - 1)/2.at n=40A135503
• a(n) = 1000*n - 20.at n=31A157515
• Indices of pentagonal pyramidal numbers which are the sum of two other such numbers: k such that A002411(k) = A002411(i)+A002411(j) for some i,j>0.at n=39A172437
• 41 times triangular numbers.at n=39A195038
• Number of length n+2 0..3 arrays with the sum of the maximum minus twice the median plus the minimum of adjacent triples multiplied by some arrangement of +-1 equal to zero.at n=5A251423
• T(n,k)=Number of length n+2 0..k arrays with the sum of the maximum minus twice the median plus the minimum of adjacent triples multiplied by some arrangement of +-1 equal to zero.at n=33A251428
• Number of length 6+2 0..n arrays with the sum of the maximum minus twice the median plus the minimum of adjacent triples multiplied by some arrangement of +-1 equal to zero.at n=2A251433
• Smallest fixed points (>0) of the base-n Kaprekar map.at n=38A319798
• Smallest fixed points (>0) of the base-2*n Kaprekar map.at n=19A319839
• Numbers k that are harmonic in Gaussian integers: k * A062327(k) is divisible by A103228(k) + i*A103229(k) (where i is the imaginary unit).at n=6A332317