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A362047
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Numbers whose prime indices satisfy: (maximum) - (minimum) = (mean).
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2
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10, 30, 39, 90, 98, 99, 100, 115, 259, 270, 273, 300, 490, 495, 517, 663, 665, 793, 810, 900, 1000, 1083, 1241, 1421, 1495, 1521, 1691, 1911, 2058, 2079, 2125, 2145, 2369, 2430, 2450, 2475, 2662, 2700, 2755, 2821, 3000, 3277, 4247, 4495, 4921, 5587, 5863, 6069
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OFFSET
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1,1
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COMMENTS
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A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
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LINKS
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FORMULA
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EXAMPLE
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The terms together with their prime indices begin:
10: {1,3}
30: {1,2,3}
39: {2,6}
90: {1,2,2,3}
98: {1,4,4}
99: {2,2,5}
100: {1,1,3,3}
115: {3,9}
259: {4,12}
270: {1,2,2,2,3}
273: {2,4,6}
300: {1,1,2,3,3}
The prime indices of 490 are {1,3,4,4}, with minimum 1, maximum 4, and mean 3, and 4-1 = 3, so 490 is in the sequence.
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MATHEMATICA
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prix[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Select[Range[100], Max@@prix[#]-Min@@prix[#]==Mean[prix[#]]&]
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PROG
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(Python)
from itertools import count, islice
from sympy import primepi, factorint
def A362047_gen(startvalue=2): # generator of terms >= startvalue
return filter(lambda n:(primepi(max(f:=factorint(n)))-primepi(min(f)))*sum(f.values())==sum(primepi(i)*j for i, j in f.items()), count(max(startvalue, 2)))
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CROSSREFS
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Partitions of this type are counted by A361862.
A243055 subtracts the least prime index from the greatest.
A326844 gives the diagram complement size of Heinz partition.
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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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