31900

Appears in sequences

• 4-dimensional analog of centered polygonal numbers. Also number of regions created by sides and diagonals of a convex n-gon in general position.at n=31A006522
• Number of regions in regular n-gon with all diagonals drawn.at n=30A007678
• Aliquot sequence starting at 660.at n=14A014362
• Numbers n such that sopf(sigma(n)) = sigma(sopf(n)), where sopf(x) = sum of the distinct prime factors of x.at n=38A076532
• a(n) = (5^n - 4^n + 3^n - 2^n)/2.at n=7A083327
• Starting positions of strings of four 9's in the decimal expansion of Pi.at n=8A083643
• Repeatedly convert from sexagesimal to centesimal, starting with 60.at n=13A097714
• Square array T(n, k) = v(k, n)((1)), where v(n, q) = M*v(n-1, q), M = {{0, 1, 0}, {0, 0, 1}, {8*q^3, 6*q, 0}}, with v(0, q) = {1, 1, 1}, read by antidiagonals.at n=49A173747
• a(n) = n*(n-3)*(n^2-7*n+14)/8.at n=22A176145
• Number of 0..n arrays x(0..3) of 4 elements without any interior element greater than both neighbors or less than both neighbors.at n=20A200872
• Number of partitions of n such that (number parts having multiplicity 1) is a part or (number of parts > 1) is a part.at n=41A241515
• a(n) = A007678(2*n+1).at n=15A341735