A143544 Triangle read by rows, T(n,k) = 2 if n is prime, 1 otherwise; 1<=k<=n.

1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2

Offset: 1

Author

Gary W. Adamson, Aug 23 2008

Keywords

• nonn
• tabl

Comments

Row sums = A143545: (1, 4, 6, 4, 10, 6, 14,...) = componentwise addition of (1, 2, 3, 4, 5,...) and A061397: (0, 2, 3, 0, 5, 0, 7,...).

Examples

			First few rows of the triangle =
1;
2, 2;
2, 2, 2;
1, 1, 1, 1;
2, 2, 2, 2, 2;
1, 1, 1, 1, 1, 1;
2, 2, 2, 2, 2, 2, 2;
...
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..11325

Crossrefs

Cf. A010051, A061397, A143536, A143545.

Programs

Mathematica

Table[1 + Boole[PrimeQ[n]], {n, 11}, {k, n}] // Flatten (* Michael De Vlieger, Oct 31 2021 *)

Formula

Triangle read by rows, T(n,k) = 2 if n is prime, 1 otherwise; 1<=k<=n.

T(n, k) = A143536(n, k) + 1. - Georg Fischer, Oct 31 2021