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 A051488 Numbers n such that phi(n) < phi(n - phi(n)). 2
 30, 60, 66, 120, 132, 138, 174, 210, 240, 246, 264, 276, 318, 330, 348, 420, 480, 492, 498, 510, 528, 534, 552, 630, 636, 660, 678, 690, 696, 786, 840, 870, 910, 960, 984, 996, 1020, 1038, 1056, 1068, 1074, 1104, 1122, 1146, 1260, 1272, 1320, 1330, 1356 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If p is a Sophie Germain prime greater than 3 and n is a natural number then 2^n*3*p is in the sequence. That is because if m= 2^n*3*p then phi(m)=2^n*(p-1) and phi(m - phi(m))=phi(2^n*3*p - 2^n*(p-1))=phi(2^n*(2p+1))=2^n*p so phi(m)phi(n)

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Last modified January 22 18:06 EST 2019. Contains 319365 sequences. (Running on oeis4.)