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A067695
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Smallest prime factor with minimal exponent in canonical prime factorization of n, a(1)=1.
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5
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1, 2, 3, 2, 5, 2, 7, 2, 3, 2, 11, 3, 13, 2, 3, 2, 17, 2, 19, 5, 3, 2, 23, 3, 5, 2, 3, 7, 29, 2, 31, 2, 3, 2, 5, 2, 37, 2, 3, 5, 41, 2, 43, 11, 5, 2, 47, 3, 7, 2, 3, 13, 53, 2, 5, 7, 3, 2, 59, 3, 61, 2, 7, 2, 5, 2, 67, 17, 3, 2, 71, 3, 73, 2, 3, 19, 7, 2, 79, 5
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OFFSET
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1,2
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LINKS
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EXAMPLE
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a(12) = a(2^2 * 3^1) = 3, but A020639(12) = 2;
a(36) = a(2^2 * 3^2) = 2 = A020639(36).
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MAPLE
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a:= n-> `if`(n=1, 1, (l-> (m-> min(map(i-> i[1], select(y->
y[2]=m, l))))(min(map(x-> x[2], l))))(ifactors(n)[2])):
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PROG
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(Python)
from sympy import factorint
if n == 1: return 1
f, g = map(tuple, zip(*sorted(factorint(n).items())))
(PARI) a(n) = if (n==1, 1, my(f=factor(n), i=vecmin(f[, 2])); f[vecmin(select(x->(x==i), f[, 2], 1)), 1]); \\ Michel Marcus, Jul 17 2023
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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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