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A053145
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When cototient function (A051953) is iterated with initial value A002110(n), a(n) = number of iterations required to reach the stationary value=0.
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0
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2, 4, 7, 11, 17, 19, 30, 31, 40, 42, 60, 64, 79, 76, 94, 124, 130, 124, 156, 172, 139, 191, 194, 220, 212, 211, 260, 268, 276, 299, 295, 320, 335, 328, 357, 366, 378, 404, 427, 438, 437, 463, 476, 492, 505, 453, 490, 541, 563, 587, 542, 599, 638, 659
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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n=6, A002110(6)=30030; the corresponding iteration chain is {30030, 24270, 17806, 9238, 4798, 2400, 1760, 1120, 736, 384, 256, 128, 64, 32, 16, 8, 4, 2, 1, 0}. Its length is 20, so a(6) = 20-1 = 19.
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MATHEMATICA
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Array[-1 + Length@ NestWhileList[# - EulerPhi@ # &, Product[Prime@ i, {i, #}], # > 0 &] &, 30] (* Michael De Vlieger, Nov 20 2017 *)
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CROSSREFS
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KEYWORD
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more,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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