A074135 - OEIS

%I #6 Dec 05 2013 19:55:33

%S 1,2,4,3,5,7,6,8,9,13,10,11,12,14,18,15,16,17,19,20,21,22,23,24,25,26,

%T 27,28,29,30,31,32,33,34,35,40,36,37,38,39,41,42,43,44,49,45,46,47,48,

%U 50,51,52,53,54,64,55,56,57,58,59,60,61,62,63,65,75,66,67,68,69,70,71

%N Triangle read by rows: for 1 <= k < n, a(n, k) is the least positive integer not already used. a(n, n) is the least positive integer not already used that makes the row sum a multiple of n.

%C Alternative (but equivalent) definition: In the following square array, numbers (not occurring earlier) are entered like this a(1, 1), a(1, 2), a(2, 1), a(3, 1), a(2, 2), a(1, 3), a(1, 4), a(2, 3), a(3, 2), a(4, 1), a(5, 1), a(4, 2), ... such that the n-th diagonal sum is a multiple of n. 1 2 7 6 18... 4 5 8 14... 3 9 12... 13 11... 10... ... sequence contains terms as they are entered.

%Y Cf. A074132, A074133, A074134, A074136.

%Y Cf. A082017, A082018, A082019, A082020.

%K nonn,easy,tabl,less

%O 1,2

%A _Amarnath Murthy_, Aug 27 2002

%E Edited and extended by _David Wasserman_, Oct 31 2006

%E Further edited by _N. J. A. Sloane_ Jan 17 2009 at the suggestion of R. J. Mathar