So there's a lot of and and & things- which do you prefer to use? I'd like to make a consistent system with these. I have found myself using n, a, 7, and & to replace and or &, and I really should just pick one. I think I'll stick with the 7 because of how convenient the key is, and how unlikely it will be to duplicate other shortforms.

s7s = signs and symptoms
o7o = on and off
of7o = off and on
c7g = comes and goes
w7w = waxes and wanes
i7d = I&D
i7dx = incision and drainage
d7c = D&C
d7cx = dilation and curettage
c7s = C&S
c7sx = culture and sensitivity
o7p = O&P
o7px = ova and parasites
a7p = A&P
a7px = auscultation and percussion
a7a = anaerobic and aerobic
a7l = amylase and lipase
ea7l = elevated amylase and lipase
a7ln = amylase and lipase are normal
a7lwnl = amylase and lipase within normal limits
a7lw = arm and leg weakness
a7mv = aortic and mitral valves
a7o = alert and oriented
a7p = abdomen and pelvis
b47a = before and after
c7d = clean and dry
f7c = fever and chills
n7v = nausea and vomitting
i7dr = incision and drainage
i7o = input and output
l7r = left and right
p7c = pros and cons
r7b = risks and benefits
p7d = prepped and draped
w7n = weakness and numbness
w7wg = waxing and waning
w7wd = waxed and waned
f7u = frequency and urgency

Huh. That's rather interesting, Georg! I use h7h for H&H. I think I have a few others like that, but they must not be common because I can't think of them at the moment. (Ever notice how your brain can't think of them, anyway.....the fingers do!) Most of the ones you listed I have no problem with in using the A, but I might swipe a few, like input and output! I think using the number as you have it is great for avoiding expansion mistakes, too.