# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a070005 Showing 1-1 of 1 %I A070005 #13 Mar 28 2015 22:36:04 %S A070005 15,21,33,35,39,42,45,51,55,57,63,65,69,75,77,78,84,85,87,91,93,95,99, %T A070005 105,110,111,114,115,117,119,123,126,129,133,135,141,143,145,147,153, %U A070005 155,156,159,161,168,170,171,175,177,183,185,186,187,189,195,201,203 %N A070005 Arithmetic mean of prime factors of n is an integer and n is neither a prime nor power of a prime. %H A070005 Reinhard Zumkeller, Table of n, a(n) for n = 1..10000 %e A070005 n=33=3*11, mean=(3+11)/2=6. %t A070005 ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] ep[x_] := Table[Part[ffi[x], 2*w], {w, 1, lf[x]}] Do[s=Apply[Plus, ba[n]]/lf[n]; If[IntegerQ[s]&&Greater[lf[n], 1], Print[n]], {n, 2, 1000}] %o A070005 (Haskell) %o A070005 a070005 n = a070005_list !! (n-1) %o A070005 a070005_list = filter ((== 0) . a010055) a078174_list %o A070005 -- _Reinhard Zumkeller_, Jun 01 2013 %o A070005 (PARI) lista(nn) = {for (n=2, nn, f = factor(n); if ((#f~ != 1) && (sum(k=1, #f~, f[k,1]) % #f~ == 0), print1(n, ", ")););} \\ _Michel Marcus_, Mar 28 2015 %Y A070005 Cf. A070006, A001414, A008472. %Y A070005 Cf. A000961, A010055; subsequence of A078174. %K A070005 easy,nonn %O A070005 1,1 %A A070005 _Labos Elemer_, Apr 11 2002 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE