math question about symbol ||

[Wounded Paw]

So I'm reading some application notes about op-amps and there's a math symbol that I don't remember.
In a simple inverting ac-coupled gain stage op-amp using a single supply and a supplied Vcc/2 bias voltage there's this term:
R3 = R1 || R2 (for minimum error due to input bias correction) for calculating resistor values.  What does the || mean, what's the math formula it represents?  I should know this but I'm drawing a blank and can't seem to find anything by searching for it.

[oskar]

So I'm reading some application notes about op-amps and there's a math symbol that I don't remember.
In a simple inverting ac-coupled gain stage op-amp using a single supply and a supplied Vcc/2 bias voltage there's this term:
R3 = R1 || R2 (for minimum error due to input bias correction) for calculating resistor values.  What does the || mean, what's the math formula it represents?  I should know this but I'm drawing a blank and can't seem to find anything by searching for it.

It means parallel to. R3 = (R1 * R2) / (R1 + R2)

[Wounded Paw]

of course, I knew I'd recognize it as soon as I saw it.
thank you.

[PRR]

It's not "math". It isn't something you missed while napping through Math class.

It is electronic-geek short-hand for what Oskar said: parallel resistance or impedance.

[metallo]

It's not "math". It isn't something you missed while napping through Math class.

Certainly was "math" at my university. http://en.wikipedia.org/wiki/Parallel_%28geometry%29