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A318305
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a(n) = Product_{primes p dividing n} p - Product_{primes p dividing n} (p-1).
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5
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0, 1, 1, 1, 1, 4, 1, 1, 1, 6, 1, 4, 1, 8, 7, 1, 1, 4, 1, 6, 9, 12, 1, 4, 1, 14, 1, 8, 1, 22, 1, 1, 13, 18, 11, 4, 1, 20, 15, 6, 1, 30, 1, 12, 7, 24, 1, 4, 1, 6, 19, 14, 1, 4, 15, 8, 21, 30, 1, 22, 1, 32, 9, 1, 17, 46, 1, 18, 25, 46, 1, 4, 1, 38, 7, 20, 17, 54, 1, 6, 1, 42, 1, 30, 21, 44, 31, 12, 1, 22, 19, 24, 33, 48, 23, 4, 1, 8
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OFFSET
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1,6
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LINKS
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FORMULA
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EXAMPLE
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For n = 45 = 3^2 * 5, the prime factors are 3 and 5, thus a(45) = (3*5) - (2*4) = 15 - 8 = 7.
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PROG
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(PARI)
A003557(n) = { my(f=factor(n)); for (i=1, #f~, f[i, 2] = f[i, 2]-1); factorback(f); }; \\ From A003557
(PARI)
A173557(n) = my(f=factor(n)[, 1]); prod(k=1, #f, f[k]-1); \\ From A173557
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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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STATUS
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approved
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