20015

Appears in sequences

• a(n) = (n+5)^3 - n^3.at n=34A038867
• Numbers k such that 10*R_k + 3 is prime, where R_k is the repunit (A002275) of length k.at n=11A056654
• Positive integers i for which A112049(i) == 8.at n=21A112068
• Number of Fermat pseudoprimes to bases 2 and 3 less than 10^n.at n=11A114246
• Binomial transform of the "1,2,3,..." triangle.at n=59A125027
• Number of ways to place zero or more nonadjacent 0,0 1,0 2,1 3,1 polyhexes in any orientation on a planar nXnXn triangular grid.at n=6A155226
• Number of n X 2 0..3 arrays with no element equal to two plus the sum of elements to its left or two plus the sum of the sum of elements above it, modulo 4.at n=5A238991
• Number of nX6 0..3 arrays with no element equal to two plus the sum of elements to its left or two plus the sum of the sum of elements above it, modulo 4.at n=1A238995
• T(n,k)=Number of nXk 0..3 arrays with no element equal to two plus the sum of elements to its left or two plus the sum of the elements above it, modulo 4.at n=22A238997
• T(n,k)=Number of nXk 0..3 arrays with no element equal to two plus the sum of elements to its left or two plus the sum of the elements above it, modulo 4.at n=26A238997
• a(n) = Sum_{k=1..n} k * A088370(n,k).at n=42A309371
• G.f.: x + x^2 / Product_{n>=1} (1 - a(n)*x^n).at n=17A345973
• Number of coprime positive integer S-unit solutions to a + b = c where a <= b < c, and where S = {prime(1), ..., prime(n)}.at n=10A362593