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Search: id:A082089
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| A082089 |
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a(n)-th prime is the fixed point if function A008472[=sum of prime factors with no repetition] is iterated when started at factorial of n-th prime. |
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1
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| 1, 3, 4, 7, 2, 13, 11, 3, 4, 3, 4, 45, 1, 60, 14, 4, 3, 3, 21, 1, 4, 4, 6, 3, 4, 3, 2, 4, 6, 2, 4, 4, 4, 4, 105, 4, 4, 3, 4, 4, 3, 4, 3, 4, 1, 4, 8, 2, 2, 19, 3, 1, 20, 14, 4, 20, 52, 4, 4, 977, 1, 3, 65, 1108, 1, 2, 46, 3, 3, 1, 3, 1, 2, 4, 829, 2, 25, 3, 8, 25, 4, 378, 3, 3, 29, 3, 6, 8, 1, 1, 28
(list; graph; listen)
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OFFSET
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2,2
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COMMENT
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a(n)<n holds usually, except few large values arising unexpectedly
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FORMULA
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a(n)=A000720[A082087[A000142(A000040[n])]]=Pi[A082087[p(n)! ]
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EXAMPLE
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n=100,p(100)=541,starts at factorial of 100th prime and ends
in 24133, the 2687th prime, so a(100)=2687;
n=99, initial value=523!, fixed point is 19, the 8th prime,
a(99)=8.
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MATHEMATICA
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ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] sopf[x_] := Apply[Plus, ba[x]] Table[PrimePi[FixedPoint[sopf, Prime[w]! ]], {w, 2, 100}]
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CROSSREFS
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Cf. A008472, A034387, A007504, A075860, A082087, A082088.
Sequence in context: A105828 A130880 A026248 this_sequence A089961 A161775 A109823
Adjacent sequences: A082086 A082087 A082088 this_sequence A082090 A082091 A082092
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Apr 09 2003
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