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A035479
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(-1)sigma sequence: a(n) = (-1)sigma(a(n-1)), where if (-1)sigma(k) = A049060(k) and a(1) = 624.
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0
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624, 696, 728, 936, 1716, 1200, 1682, 869, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480, 488, 780, 480
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OFFSET
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1,1
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COMMENTS
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This sequence becomes a cycle of period 3: 780, 480, 488. It is called a (-1)sigma sociable group of order 3.
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LINKS
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EXAMPLE
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Factorizations: 2^4*3*13, 2^3*3*29, 2^3*7*13, 2^3*3^2*13, 2^2*3*11*13, 2^4*3*5^2, 2*29^2, 11*79, 2^2*3*5*13, 2^5*3*5, 2^3*61.
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MATHEMATICA
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f[p_, e_] := (p^(e + 1) - 1)/(p - 1) - 2; s[n_] := Times @@ f @@@ FactorInteger[n]; s[1] = 1; NestList[s, 624, 50] (* Amiram Eldar, Aug 26 2022 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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