OK, Neomails went out recently.
Congratulations! You have guessed correctly in the Lenny Conundrum game (round 350). You have won 754 NP!
Because you were in the first 250 to guess correctly, you also have been awarded a Guide To Your Health, and receive a trophy and the Lenny Conundrum avatar!
Answer was 140.
How I personally solved it. It's not the most efficient way, but it helped me to think about what I was doing.
I did the first few by hand, and made up an arbitrary time for when the infections started (12:00). OK, so at 12:00, one Neopet was infected. Then, at 12:05, that one Neopet affected another, so 2 total were infected. Then at 12:10, those 2 affected 2 more, so 4 total were affected. So, the formula was log base 2 of "number of Neopets" (somewhere over 262 million, according to
http://www.neopets.com/petcentral.phtml) * 5 (minutes). I used the calculator at
http://logbase2.blogspot.com/2008/08/log-calculator.html to determine the log base 2 number. That gives 27.96. Don't forget to round up! Rounding down would not affect every Neopet. So, it's 28 * 5 = 140.