[seqfan] Condom sequence

[Tanya Khovanova]

Hello all,

I just wrote a piece that might contain a new sequence:
http://blog.tanyakhovanova.com/?p=168

The sequence is related to the generalization of the following math problem:

Suppose three gay men all want to have sex with each other and every pair among them wants to do two penetrative sexual acts, switching roles. They want to avoid contaminating each other, and in addition, each man also does not want to cross-contaminate himself from either region to the other. How can they do that using exactly three condoms?

a(2) = 2,
a(3) = 3,
a(4) = 4.