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%I #7 Aug 24 2012 10:49:57
%S 1,2,3,4,6,7,8,10,11,12,13,15,18,20,21,22,24,27,28,29,30
%N Sum of the numbers of the matrix A111490 along a boustrophedon path: a11, a11+a21, a11+a21+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+2, 1+1+1+1+2+1+1+2+1, 1+1+1+1+2+1+1+2+1+1, ...
%e That is 1, 2, 3, 4, 6, 7, 8, 10, 11, 12, 13, 15, 18, 20, etc.
%Y Cf. A119930.
%K nonn,easy
%O 0,2
%A _Paolo P. Lava_ and _Giorgio Balzarotti_, May 30 2006