A167991 Blocks of size 2n, each with 2n-1 replicas of 2n followed by 2n+1; n=1, 2, 3, ...

2, 3, 4, 4, 4, 5, 6, 6, 6, 6, 6, 7, 8, 8, 8, 8, 8, 8, 8, 9, 10, 10, 10, 10, 10, 10, 10, 10, 10, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 17, 18, 18, 18, 18

Offset: 1

Author

Paul Curtz, Nov 16 2009

Keywords

• nonn
• easy

Comments

First differences of A167381.

The sum of the terms in block n is 4*n^2+1 = A053755(n).

Examples

			(2, 3), (4, 4, 4, 5), (6, 6, 6, 6, 6, 7), (8, 8, 8, 8, 8, 8, 8, 9), ...
		

Programs

Mathematica

r[1] = Range[4];
r[n_] := r[n] = Range[r[n-1][[-1]]+1, r[n-1][[-1]] + (2n)^2];
s[n_] := Partition[r[n], Sqrt[Length[r[n]]]][[All, n]];
A167991 = Table[s[n], {n, 1, 9}] // Flatten // Differences (* Jean-François Alcover, Mar 27 2017 *)