A119930 - OEIS

%I #6 Aug 24 2012 10:49:57

%S 1,2,3,4,6,7,8,9,11,12,13,15,18,20,21,22,23,24,27,29,30

%N Sum of the numbers of the matrix A111490 along a boustrophedon path: a11, a11+a12, a11+a12+a21, etc.

%D G. Balzarotti and P. P. Lava, Le sequenze di numeri interi, Hoepli, 2008, p. 60.

%e If we rewrite the matrix putting on the top the upper left edge and then we sum the numbers following a boustrophedon path we have:

%e .............1.\

%e ..........._____\

%e ........../1...1.

%e ........./_________

%e .........1...2...1.\

%e ......______________\

%e ...../.1...2...1...1.

%e ..../__________________

%e .....1...2...3...2...1.\

%e ..______________________\

%e ..1...2...3...1...1...1.

%e then

%e 1, 1+1, 1+1+1, 1+1+1+1, 1+1+1+1+2, 1+1+1+1+2+1, 1+1+1+1+2+1+1, 1+1+1+1+2+1+1+1, 1+1+1+1+2+1+1+1+2, 1+1+1+1+2+1+1+1+2+1, ...

%e That is 1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 15, 18, 20, etc.

%Y Cf. A119931.

%K nonn,easy

%O 0,2

%A _Paolo P. Lava_ and _Giorgio Balzarotti_, May 30 2006