OFFSET
0,3
COMMENTS
EXAMPLE
Illustration of one of the three views with seven shells:
.
. . . . . 1 . . . .
. . . . 2 1 . . . .
. Table 2.0 . 3 . . 1 2 . . . Table 2.1
. . . 2 2 1 . . 3 .
. . . . . 1 2 2 . .
. 1 . . . .
.
The sum of parts that are visible is 1+1+1+1+1+1+1+2+2+2+2+2+2+2+3+3+3+3+4+4+5+6+7 = 59, so a(7) = 59. Using the formula we have a(7) = 7+24+28 = 59.
CROSSREFS
KEYWORD
nonn
AUTHOR
Omar E. Pol, Jan 27 2012
STATUS
approved