login
A261030
Numbers k such that sqrt(k + sqrt(k + sqrt(k + ...))) is an even perfect number.
0
30, 756, 245520, 66056256, 1125625012162560, 73785850390636462080, 18889393873815823712256, 5316911978187903333320785637991776256
OFFSET
1,1
LINKS
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
Sequence in context: A089507 A045689 A096722 * A160269 A367275 A367332
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Aug 07 2015
STATUS
approved