23047

Appears in sequences

• a(n) = 1*t(n) + 2*t(n-1) + ... + k*t(n+1-k), where k=floor((n+1)/2) and t = A000032 (Lucas numbers).at n=16A023861
• Interprimes which are of the form s*prime, s=19.at n=4A075294
• a(n) is the position of a(n-1) in the decimal expansion of Pi, starting with a(1)=13.at n=15A119744
• L.g.f.: Sum_{n>=1} a(n)*x^n/n = Sum_{n>=1} x^n/n * exp( Sum_{k>=1} sigma(n*k)*x^(n*k)/k ).at n=22A203321
• Number of n X 2 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or left-upward diagonal neighbors.at n=4A208858
• Number of nX5 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or left-upward diagonal neighbors.at n=1A208861
• T(n,k)=Number of nXk 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or left-upward diagonal neighbors.at n=16A208864
• T(n,k)=Number of nXk 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or left-upward diagonal neighbors.at n=19A208864
• Number of (w,x,y,z) with all terms in {1,...,n} and 3w=x+y+z+n.at n=38A212247
• Integers k such that A072473(k) = A072473(k+1) = A072473(k+2) = A072473(k+3).at n=4A255172
• a(n) = Sum of (Y(2,p)^2) over the partitions p of n, Y(2,p) = number of part sizes with multiplicity 2 or greater in p.at n=30A302347