1,1

Ultraperfect numbers (A139306) minus 1.

a(n) = (2^(2*A000043(n) - 1)) - 1 = A139306(n) - 1.

a(5)=33554431 because A000043(5)=13 and (2^(2*13 - 1))-1 = 2^25 - 1 = 33554431.

Cf. A139287, A139295, A139306.

Sequence in context: A153028 A135630 A139287 this_sequence A134709 A139314 A163083

Adjacent sequences: A139304 A139305 A139306 this_sequence A139308 A139309 A139310

nonn

Omar E. Pol (info(AT)polprimos.com), Apr 13 2008, May 08 2008