A261030 Numbers k such that sqrt(k + sqrt(k + sqrt(k + ...))) is an even perfect number.

30, 756, 245520, 66056256, 1125625012162560, 73785850390636462080, 18889393873815823712256, 5316911978187903333320785637991776256

Offset

1,1

Links

Table of n, a(n) for n=1..8.

Eric Weisstein's World of Mathematics, PerfectNumber

Formula

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

Example

For n = 1, a(1) = 30 since sqrt(30 + sqrt(30 + sqrt(30 + ...))) = 6, which is an even perfect number.

Crossrefs

Cf. A000396, A000043.

Sequence in context: A089507 A045689 A096722 * A160269 A367275 A367332

Adjacent sequences: A261027 A261028 A261029 * A261031 A261032 A261033

Keyword

nonn

Author

Ilya Gutkovskiy, Aug 07 2015

Status

approved