A256230 Numbers n such that neither n nor 2*n is representable as x*y+x+y, where x>=y>1.
0, 1, 2, 3, 5, 6, 9, 18, 21, 30, 33, 36, 78, 81, 96, 105, 138, 141, 156, 165, 198, 210, 228, 261, 270, 273, 306, 330, 336, 345, 366, 378, 393, 438, 453, 498, 525, 546, 561, 576, 585, 600, 606, 618, 660, 690, 726, 765, 810, 828, 861, 876, 933, 936, 966, 996, 1005, 1008
Offset: 1
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Programs
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Python
TOP = 2200 a = [0]*TOP for y in range(2, TOP//2): for x in range(y, TOP//2): k = x*y + x + y if k>=TOP: break a[k]=1 print([n for n in range(TOP//2) if a[n]==0 and a[2*n]==0])