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%I #6 Mar 30 2012 17:23:03
%S 1,2,3,4,6,7,8,12,16,19,22,24,28,31,32,43,48,64,76,79,96,103,112,128,
%T 139,142,163,166,184,192,199,211,223,256,262,268,271,283,304,307,316,
%U 331,352,367,376,379,384,412,439,448,454,463,496,499,512,526,547
%N Indices of hexagonal numbers that are not the difference of two positive hexagonal numbers.
%t Select[Range[600], Reduce[#*(2*#-1) == x*(2*x-1) - y*(2*y-1) && x > 0 && y > 0, {x, y}, Integers] == False &]
%Y Cf. A000384 (hexagonal numbers), A135768 (pentagonal case).
%K nonn
%O 1,2
%A _T. D. Noe_, Dec 06 2011
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