Ultraperfect numbers (A139306), divided by 2.
Also, a(n) is the largest proper divisor of the n-th ultraperfect number.
Table of n, a(n) for n=1..8.
a(n) = A139306(n)/2.
Cf. A000043, A139288, A139306, A152922, A152923.
Sequence in context: A200045 A099202 A139288 * A215116 A212297 A152153
Adjacent sequences: A152918 A152919 A152920 * A152922 A152923 A152924
Omar E. Pol, Dec 15 2008