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1, 3, 2, 6, 5, 4, 10, 23, 12, 7, 39, 9, 97, 24, 164, 484, 2759, 5044, 109, 32334, 114605, 216960, 8, 14, 252, 785135, 5503557, 28, 39222428, 75703838, 548300521, 1496, 2063337476, 4008153424, 29523940595, 3858, 112174606866, 834662735468, 11
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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This sequence is a permutation of the positive integers. It is its own inverse permutation.
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LINKS
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FORMULA
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EXAMPLE
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The primes raised to prime exponents form the sequence, when the terms are arranged in numerical order, 4,8,9,25,27,32,49,121,125,128,...(sequence A053810). The 10th term is 128, which is 2^7. So the 10th term of sequence A145521 is 7^2 = 49. 49 is the 7th term of A053810. So a(10) = 7 and a(7) = 10.
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PROG
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(PARI) lista(nn) = {my(c, m); for(k=1, nn, if(isprime(isprimepower(k, &p)), c=0; m=bigomega(k)^p; forprime(q=2, sqrtint(m), c+=primepi(logint(m, q))); print1(c, ", "))); } \\ Jinyuan Wang, Feb 25 2020
(Python)
from itertools import count
from sympy import integer_nthroot, isprime, primepi
total = 0
for p in count(2):
if isprime(p): total += primepi(integer_nthroot(A145521(n), p)[0])
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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