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0, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 3, 3, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 2, 1, 1, 3, 1, 1, 1, 1, 1, 5, 1, 1, 2, 3, 1, 1, 2, 1, 2, 1, 1, 2, 1, 1, 1, 2, 2, 1, 1, 1, 2, 1, 1, 5, 1, 1, 1, 3, 2, 3, 1, 1, 1, 1, 1, 4, 2, 1, 2, 1, 1, 2, 2, 1, 2, 1, 2, 1, 1, 3, 1, 1, 1, 1, 1, 1, 3
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,4
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LINKS
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EXAMPLE
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28 has a prime-factorization of: 2^2 * 7^1. The sum of the distinct primes dividing 28 is 2+7 = 9. The sum of the exponents in the prime-factorization of 28 is 2+1 = 3. a(28) therefore equals gcd(9,3) = 3.
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MAPLE
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A008472 := proc(n) if n = 1 then 0 ; else add(p, p= numtheory[factorset](n)) ; end if ; end proc:
A161606 := proc(n) igcd(A008472(n), numtheory[bigomega](n)) ; end proc:
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MATHEMATICA
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Table[GCD[DivisorSum[n, # &, PrimeQ], PrimeOmega@ n], {n, 105}] (* Michael De Vlieger, Jul 20 2017 *)
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PROG
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(Python)
from sympy import primefactors, gcd
def a001222(n): return 0 if n==1 else a001222(n//primefactors(n)[-1]) + 1
def a(n): return gcd(sum(primefactors(n)), a001222(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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EXTENSIONS
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Term a(1)=0 prepended and more terms computed by Antti Karttunen, Jul 20 2017
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STATUS
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approved
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