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A058653
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Numbers k such that sigma(phi(k)) = phi(sigma(k)-k).
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0
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2, 18, 50, 1250, 1980, 6900, 61080, 1369020, 2025660, 2820240, 4003230, 4917360, 8597316, 15396360, 15893010, 28725648, 41427360, 53423760, 148663020, 209752500, 212019024, 222746160, 232210080, 281870316, 298848144, 314121180, 322230180, 385612260, 390760260
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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Select[ Range[ 10^6 ], DivisorSigma[ 1, EulerPhi[ # ] ] == EulerPhi[ DivisorSigma[ 1, # ] - # ] & ]
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PROG
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(Python)
from sympy import divisor_sigma as sigma, totient as phi
def aupto(limit):
for k in range(2, limit):
if sigma(phi(k)) == phi(sigma(k) - k): print(k, end=", ")
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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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