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A244974
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Sum of numbers m <= n whose set of prime divisors is a subset of the set of prime divisors of n.
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5
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1, 3, 4, 7, 6, 16, 8, 15, 13, 30, 12, 45, 14, 36, 33, 31, 18, 79, 20, 66, 41, 64, 24, 103, 31, 70, 40, 80, 30, 235, 32, 63, 84, 114, 73, 198, 38, 120, 92, 163, 42, 310, 44, 140, 130, 132, 48, 246, 57, 213, 108, 154, 54, 300, 97, 217, 116, 150, 60, 600, 62, 156, 180, 127, 109, 540, 68, 246
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OFFSET
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1,2
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COMMENTS
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a(n) = A000203(n) when n is prime or a perfect prime power (A000961). This is because all products of the prime divisor p in such numbers produce divisors.
a(n) > A000203(n) when n is composite and not a perfect prime power.
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LINKS
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FORMULA
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a(n) = Sum_{k=1..n} k*( floor(n^k/k)-floor((n^k - 1)/k) ). - Anthony Browne, May 25 2016
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EXAMPLE
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For n = 4, A162306(4) = {1, 2, 4} and a(4) = 7.
For n = 5, A162306(5) = {1, 5} and a(5) = 6.
For n = 6, A162306(6) = {1, 2, 3, 4, 6} and a(6) = 16.
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MATHEMATICA
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Table[Total@ Union[{1}, Function[d, Select[Range@ n, Union[d, First /@ FactorInteger@ #] == d &]][First /@ FactorInteger@ n]], {n, 68}] (* or *)
Table[Sum[k (Floor[n^k/k] - Floor[(n^k - 1)/k]), {k, n}], {n, 68}] (* Michael De Vlieger, May 26 2016 *)
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PROG
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(PARI) a(n) = {summ = 0; spn = factor(n)[, 1]~; for (m=1, n, spm = factor(m)[, 1]~; if (setintersect(spm, spn) == spm, summ += m); ); summ; } \\ Michel Marcus, Jul 17 2014
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CROSSREFS
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a(n) = sum of terms of n-th row of triangle A162306(n,k).
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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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