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A335940
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a(n) = n if n is prime, a(n) = 0 if n is a nontrivial power of a prime, and otherwise a(n) = max{|p-q| where p, q are distinct primes dividing n}.
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1
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1, 2, 3, 0, 5, 1, 7, 0, 0, 3, 11, 1, 13, 5, 2, 0, 17, 1, 19, 3, 4, 9, 23, 1, 0, 11, 0, 5, 29, 3, 31, 0, 8, 15, 2, 1, 37, 17, 10, 3, 41, 5, 43, 9, 2, 21, 47, 1, 0, 3, 14, 11, 53, 1, 6, 5, 16, 27, 59, 3, 61, 29, 4, 0, 8, 9, 67, 15, 20, 5, 71, 1, 73, 35, 2, 17, 4, 11, 79, 3, 0, 39, 83
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OFFSET
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1,2
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LINKS
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FORMULA
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EXAMPLE
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a(12) = 1 because its prime factors (2x2x3) have a maximum difference of 1 (3-2).
a(14) = 5 because its prime factors (2x7) have a maximum difference of 5 (7-2).
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PROG
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(Python)
import numpy as np
def primeFactors(n):
x=[]
while n % 2 == 0:
x.append(2),
n = n / 2
for i in range(3, int(np.sqrt(n))+1, 2):
while n % i== 0:
x.append(i),
n = n / i
if n > 2:
x.append(n)
if len(x)==0:
x.append(1)
if len(x)!=1:
y=x[-1]-x[0]
else:
y=x[0]
return y
print(len(x))
nums = list(range(1, 101))
final=[]
for i in nums:
final.append(primeFactors(i))
final = [int(i) for i in final]
print(final)
(Python)
from sympy import primefactors, isprime
if isprime(n):
return n
else:
pf = primefactors(n)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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