1,1

There are 20 rectangular parallelepipeds with integer edges such that increasing each edge by 2 doubles the volume, sorted in increasing volume: {6,8,10}, {6,7,12}, {5,8,14}, {6,6,16}, {5,7,18}, {4,12,14}, {4,10,18}, {4,9,22}, {5,6,28}, {4,8,30}, {3,20,22}, {3,18,25}, {3,16,30}, {4,7,54}, {3,15,34}, {3,14,40}, {3,13,50}, {5,5,98}, {3,12,70}, {3,11,130}

The third smallest product of abc such that (a+2)(b+2)(c+2)=2abc is 560, so a(3)=560.

Sequence in context: A056987 A025025 A108256 this_sequence A019287 A108876 A083728

Adjacent sequences: A115154 A115155 A115156 this_sequence A115158 A115159 A115160

fini,full,nonn

Graeme McRae (g_m(AT)mcraefamily.com), Jan 14 2006