A175761 - OEIS

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A175761

Odd nonprimes such that the arithmetic mean of all prime factors is not an integer.

1, 45, 63, 75, 99, 117, 135, 147, 153, 165, 171, 175, 207, 245, 255, 261, 273, 279, 315, 325, 333, 345, 351, 363, 369, 375, 385, 387, 399, 405, 423, 435, 455, 459, 475, 477, 495, 507, 531, 539, 549, 561, 567, 595, 603, 615, 639, 651, 657, 665, 675, 705, 711, 715, 735

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

The presence of 1 (which has no prime factors) is for compatibility with A175352.

LINKS

G. C. Greubel, Table of n, a(n) for n = 1..5000

FORMULA

Equals: Intersection of A175352 and A014076.

EXAMPLE

a(6) = 117 because 117 = 3*3*13 and (3 + 3 + 13)/3 is not an integer.

MATHEMATICA

fQ[n_] := Block[{fi = Flatten[ Table[ #[[1]], {#[[2]]}] & /@ FactorInteger@ n]}, len = Length@ fi; len != 1 && ! IntegerQ[ Plus @@ fi/len]]; Join[{1}, Select[1 + 2 Range@ 356, fQ]] (* Robert G. Wilson v, Aug 31 2010 *)

CROSSREFS

Cf. A141468, A175352.

Sequence in context: A077646 A230577 A336555 * A360769 A046364 A321498

Adjacent sequences: A175758 A175759 A175760 * A175762 A175763 A175764

KEYWORD

nonn,easy

AUTHOR

Juri-Stepan Gerasimov, Aug 29 2010

EXTENSIONS

Corrected (315, 345 inserted, 355 removed) by R. J. Mathar, Aug 30 2010

STATUS

approved