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A076531 Numbers n such that sopf(phi(n)) = phi(sopf(n)), where sopf(x) = sum of the distinct prime factors of x. 8
3, 203, 322, 377, 644, 851, 931, 1166, 1211, 1288, 1421, 1666, 1815, 1862, 2332, 2576, 3332, 3724, 4664, 4830, 5152, 6401, 6517, 6664, 7042, 7241, 7448, 9075, 9328, 9555, 9660, 9845, 9922, 9947, 10304, 10465, 11662, 11814, 11830, 12558, 12903, 13034 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
sopf(phi(203)) = sopf(168) = 12; phi(sopf(203)) = phi(36) = 12 hence 203 is a term of the sequence.
MATHEMATICA
p[n_] := Apply[Plus, Transpose[FactorInteger[n]][[1]]]; Select[Range[3, 10^4], p[EulerPhi[ # ]] == EulerPhi[ p[ # ]] &]
PROG
(PARI) sopf(n) = my(f=factor(n)); sum(j=1, #f~, f[j, 1]); \\ A008472
isok(n) = eulerphi(sopf(n)) == sopf(eulerphi(n)); \\ Michel Marcus, Oct 04 2019
CROSSREFS
Sequence in context: A229602 A080297 A080274 * A269552 A038789 A212997
KEYWORD
nonn
AUTHOR
Joseph L. Pe, Oct 18 2002
EXTENSIONS
Edited and extended by Ray Chandler, Feb 13 2005
STATUS
approved

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Last modified February 21 06:16 EST 2024. Contains 370219 sequences. (Running on oeis4.)