def pe21(limit=10000):
"""
>>> pe21()
(31626, [(220, 284), (1184, 1210), (2620, 2924), (5020, 5564), (6232, 6368)])
"""
ami = []
s = 0
for i in range(2, limit + 1):
t = spd(i)
if i < t and i == spd(t):
s += i + t
ami.append((i, t))
return (s, ami)
def pe21(limit=10000):
"""
>>> pe21()
(31626, [(220, 284), (1184, 1210), (2620, 2924), (5020, 5564), (6232, 6368)])
"""
ami = []
s = 0
for i in range(2, limit + 1):
t = spd(i)
if i < t and i == spd(t):
s += i + t
ami.append((i, t))
return (s, ami)
def pe23(limit=28123):
"""
>>> pe23()
4179871
"""
s = 0
abn = set()
for n in range(1, limit):
if spd(n) > n:
abn.add(n)
if not any((n - a in abn) for a in abn):
s += n
return s
