cp's OEIS Frontend

A261698 Irregular triangle read by rows in which row n lists the odd divisors of n in the order as follows: the smallest, the largest, the second smallest, the second largest, the third smallest, the third largest, and so on.

%I A261698 #25 Jul 27 2017 03:41:41
%S A261698 1,1,1,3,1,1,5,1,3,1,7,1,1,9,3,1,5,1,11,1,3,1,13,1,7,1,15,3,5,1,1,17,
%T A261698 1,9,3,1,19,1,5,1,21,3,7,1,11,1,23,1,3,1,25,5,1,13,1,27,3,9,1,7,1,29,
%U A261698 1,15,3,5,1,31,1,1,33,3,11,1,17,1,35,5,7,1,9,3,1,37,1,19,1,39,3,13,1,5,1,41,1,21,3,7,1,43,1,11,1,45,3,15,5,9
%N A261698 Irregular triangle read by rows in which row n lists the odd divisors of n in the order as follows: the smallest, the largest, the second smallest, the second largest, the third smallest, the third largest, and so on.
%C A261698 Also the odd numbers of A210959.
%C A261698 Row lengths give A001227.
%C A261698 Row sums give A000593.
%C A261698 Another version of A182469 from which differs at a(14), or T(9,2).
%C A261698 For a similar version see A261697 from which differs at a(34), or T(18,2).
%e A261698 List of divisors of 45 from distinct sequences:
%e A261698 45th row of triangle A182469: 1, 3, 5, 9, 15, 45.
%e A261698 45th row of triangle A261697: 1, 45, 3, 5, 15, 9.
%e A261698 45th row of this triangle...: 1, 45, 3, 15, 5, 9.
%e A261698 Triangle begins:
%e A261698   1;
%e A261698   1;
%e A261698   1,  3;
%e A261698   1;
%e A261698   1,  5;
%e A261698   1,  3;
%e A261698   1,  7;
%e A261698   1;
%e A261698   1,  9,  3;
%e A261698   1,  5;
%e A261698   1, 11;
%e A261698   1,  3;
%e A261698   1, 13;
%e A261698   1,  7;
%e A261698   1, 15,  3,  5;
%e A261698   1;
%e A261698   1, 17;
%e A261698   1,  9,  3;
%e A261698   1, 19;
%e A261698   1,  5;
%e A261698   1, 21,  3,  7;
%e A261698   ...
%Y A261698 Cf. A000593, A001227, A027750, A182469, A210959, A261697.
%K A261698 nonn,tabf
%O A261698 1,4
%A A261698 _Omar E. Pol_, Sep 21 2015