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A357852
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Replace prime(k) with prime(k+2) in the prime factorization of n.
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4
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1, 5, 7, 25, 11, 35, 13, 125, 49, 55, 17, 175, 19, 65, 77, 625, 23, 245, 29, 275, 91, 85, 31, 875, 121, 95, 343, 325, 37, 385, 41, 3125, 119, 115, 143, 1225, 43, 145, 133, 1375, 47, 455, 53, 425, 539, 155, 59, 4375, 169, 605, 161, 475, 61, 1715, 187, 1625, 203
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OFFSET
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1,2
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COMMENTS
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This is the same as A045966 except the first term is 1 instead of 3.
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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:
1: {}
5: {3}
7: {4}
25: {3,3}
11: {5}
35: {3,4}
13: {6}
125: {3,3,3}
49: {4,4}
55: {3,5}
17: {7}
175: {3,3,4}
19: {8}
65: {3,6}
77: {4,5}
625: {3,3,3,3}
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MATHEMATICA
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primeMS[n_]:=If[n==1, {}, Flatten[Cases[FactorInteger[n], {p_, k_}:>Table[PrimePi[p], {k}]]]];
Table[Product[Prime[i+2], {i, primeMS[n]}], {n, 30}]
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PROG
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(PARI) a(n) = my(f=factor(n)); for (k=1, #f~, f[k, 1] = nextprime(nextprime(f[k, 1]+1)+1)); factorback(f); \\ Michel Marcus, Oct 28 2022
(Python)
from math import prod
from sympy import nextprime, factorint
def A357852(n): return prod(nextprime(p, ith=2)**e for p, e in factorint(n).items()) # Chai Wah Wu, Oct 29 2022
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CROSSREFS
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Applying the transformation only once gives A003961.
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KEYWORD
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nonn,mult
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AUTHOR
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STATUS
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approved
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