[seqfan] Re: A051501

[Hans Havermann]

Richard Mathar:

> http://primes.utm.edu/curios/page.php/137438953481.html
> shows only two 7's and more digits, 1.25164 75977 90463 01759 44320  
> 53623,
> so I'd think that the Well's quotation is a misprint .

The constant appears necessarily to be derived from the largest known  
term of the sequence: a(4) = 137438953481.

Floor[2^2^2^2^1.2516475977904] = 137438953480
Floor[2^2^2^2^1.2516475977905] = 137438953481
Floor[2^2^2^2^1.2516475977906] = 137438953482

So, the more accurate description on the Prime Curios page is just a  
*lower limit* that guarantees a(4).