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A367584
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Least number whose multiset multiplicity kernel (in which each prime exponent becomes the least prime factor with that exponent) is n. First position of n in A367580.
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13
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1, 2, 3, 6, 5, 12, 7, 30, 15, 20, 11, 90, 13, 28, 45, 210, 17, 60, 19, 150, 63, 44, 23, 630, 35, 52, 105, 252, 29, 360, 31, 2310, 99, 68, 175, 2100, 37, 76, 117, 1050, 41, 504, 43, 396, 525, 92, 47, 6930, 77, 140, 153, 468, 53, 420, 275, 1470, 171, 116, 59
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OFFSET
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1,2
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COMMENTS
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We define the multiset multiplicity kernel (MMK) of a positive integer n to be the product of (least prime factor with exponent k)^(number of prime factors with exponent k) over all distinct exponents k appearing in the prime factorization of n. For example, 90 has prime factorization 2^1 * 3^2 * 5^1, so for k = 1 we have 2^2, and for k = 2 we have 3^1, so MMK(90) = 12. As an operation on multisets, MMK is represented by the triangle A367579, and as an operation on their ranks it is represented by A367580.
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LINKS
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FORMULA
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a(p) = p for all primes p.
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EXAMPLE
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The least number with multiset multiplicity kernel 9 is 15, so a(9) = 15.
The terms together with their prime indices begin:
1 -> 1: {}
2 -> 2: {1}
3 -> 3: {2}
4 -> 6: {1,2}
5 -> 5: {3}
6 -> 12: {1,1,2}
7 -> 7: {4}
8 -> 30: {1,2,3}
9 -> 15: {2,3}
10 -> 20: {1,1,3}
11 -> 11: {5}
12 -> 90: {1,2,2,3}
13 -> 13: {6}
14 -> 28: {1,1,4}
15 -> 45: {2,2,3}
16 ->210: {1,2,3,4}
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MATHEMATICA
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nn=1000;
mmk[q_]:=With[{mts=Length/@Split[q]}, Sort[Table[Min@@Select[q, Count[q, #]==i&], {i, mts}]]];
spnm[y_]:=Max@@NestWhile[Most, Sort[y], Union[#]!=Range[Max@@#]&];
qq=Table[Times@@mmk[Join@@ConstantArray@@@FactorInteger[n]], {n, nn}];
Table[Position[qq, i][[1, 1]], {i, spnm[qq]}]
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CROSSREFS
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Positions of squarefree numbers are A000961.
Contains no nonprime prime powers A246547.
Positions of first appearances in A367580.
A071625 counts distinct prime exponents.
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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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