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A177204 Pseudoperfect totient numbers (A288452) which are not powers of primes (A000961). 1
15, 33, 35, 39, 51, 55, 65, 69, 77, 85, 87, 111, 115, 119, 123, 141, 143, 153, 155, 159, 161, 175, 177, 183, 187, 201, 205, 209, 213, 219, 221, 235, 245, 247, 249, 253, 255, 265, 267, 287, 291, 295, 299, 303, 305, 309, 319, 321, 323, 325, 327, 329, 339, 341, 363, 371, 377, 391, 393, 403, 407, 411, 413, 415 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
A proper subset of A288452. All odd primes and all powers of 3 are pseudoperfect totient numbers. First term which has k factors counting multiplicity >1: 15, 153, 875, 4375, 62451, etc. First term which has k distinct factors >1: 15, 255, 21505, etc.
LINKS
MATHEMATICA
fQ[n_] := Module[{tots = Rest@ NestWhileList[ EulerPhi, n, # > 1 &]}, MemberQ[Total /@ Subsets[tots, Length[ tots]], n]]; Select[ Range[ 3, 440, 2], fQ@# && !PrimePowerQ@# &]
CROSSREFS
Sequence in context: A331551 A180815 A336625 * A342193 A343338 A302697
KEYWORD
nonn,easy
AUTHOR
STATUS
approved

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Last modified June 15 01:02 EDT 2024. Contains 373402 sequences. (Running on oeis4.)