Formula to calculate probability that I will be interrupted whilst writing.

Formula to calculate probability that I will be interrupted whilst writing, specifically that wife [insert significant other suitable to your case] will call all available numbers until reaching me.

ω = wife

N = number of phone calls.

Ι = me, aka iota.  Not one iota.  Not in this formula.

Ω = Omega.  Just a nice looking symbol that resembles either a horseshoe or the Stargate, depending on what channels you watch.  Also not in this formula.

Pr[ω]=N!/ω!(N−ω!) * πω(1−π)N−ω