A140685 Triangle T(n,k) read by rows: T(n,k) = 1 if n is odd and k=(n-1)/2; T(n,k) = 2 otherwise.

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

Offset: 1

Author

Roger L. Bagula and Mats Granvik, Jul 11 2008

Keywords

• nonn
• tabl
• easy

Comments

Row sums give A042948.

Examples

			The triangle starts in row n=1 with columns 0 <= k < n as:
  1;
  2, 2;
  2, 1, 2;
  2, 2, 2, 2;
  2, 2, 1, 2, 2;
  2, 2, 2, 2, 2, 2;
  2, 2, 2, 1, 2, 2, 2;
  2, 2, 2, 2, 2, 2, 2, 2;
  2, 2, 2, 2, 1, 2, 2, 2, 2;
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2;
		

Links

• Antti Karttunen, Table of n, a(n) for n = 1..10440; the first 144 rows of the triangle

Crossrefs

Cf. A002024, A002260, A104041.

Programs

Scheme

(define (A140685 n) (A140685tr (A002024 n) (- (A002260 n) 1)))
(define (A140685tr n k) (if (and (odd? n) (= k (/ (- n 1) 2))) 1 2))

Extensions

Definition simplified by the Assoc. Eds. of the OEIS, Oct 12 2010

More terms from Antti Karttunen, Oct 10 2017