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

1,2

Comments

Row sums give A042948.

Links

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

Example

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;

Prog

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

Crossrefs

Cf. A002024, A002260, A104041.

Sequence in context: A276788 A282625 A026498 * A055666 A251139 A195061

Adjacent sequences: A140682 A140683 A140684 * A140686 A140687 A140688

Keyword

nonn,tabl,easy

Author

Roger L. Bagula and Mats Granvik, Jul 11 2008

Extensions

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

More terms from Antti Karttunen, Oct 10 2017

Status

approved