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A286253
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Compound filter: a(n) = P(A055396(n), A001511(1+n)), where P(n,k) is sequence A000027 used as a pairing function.
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4
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0, 1, 8, 1, 9, 1, 25, 1, 5, 1, 26, 1, 27, 1, 17, 1, 35, 1, 53, 1, 5, 1, 75, 1, 9, 1, 8, 1, 65, 1, 131, 1, 5, 1, 13, 1, 90, 1, 12, 1, 104, 1, 134, 1, 5, 1, 186, 1, 14, 1, 8, 1, 152, 1, 18, 1, 5, 1, 188, 1, 189, 1, 30, 1, 9, 1, 229, 1, 5, 1, 273, 1, 252, 1, 8, 1, 14, 1, 347, 1, 5, 1, 323, 1, 9, 1, 12, 1, 324, 1, 19, 1, 5, 1, 31, 1, 350, 1, 8, 1, 377, 1, 462, 1, 5
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OFFSET
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1,3
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LINKS
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FORMULA
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PROG
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(PARI)
for(n=1, 10000, write("b286253.txt", n, " ", A286253(n)));
(Python)
from sympy import primepi, isprime, primefactors
def T(n, m): return ((n + m)**2 - n - 3*m + 2)/2
def a049084(n): return primepi(n)*(1*isprime(n))
def a055396(n): return 0 if n==1 else a049084(min(primefactors(n)))
def a001511(n): return 2 + bin(n - 1)[2:].count("1") - bin(n)[2:].count("1")
def a(n): return T(a055396(n), a001511(n + 1)) # Indranil Ghosh, May 07 2017
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CROSSREFS
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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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