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A239546 Sum of the prime factors of n, where n runs through perfect numbers. 1


%S 5,9,33,129,8193,131073,524289,2147483649,2305843009213693953,

%T 618970019642690137449562113,162259276829213363391578010288129,

%U 170141183460469231731687303715884105729

%N Sum of the prime factors of n, where n runs through perfect numbers.

%F a(n) = A008472(A000396(n)). - _Michel Marcus_, Mar 21 2014

%F a(n) = A000668(n) + 2 (conjectured). - _Michel Marcus_, Mar 21 2014

%e First perfect number is 6, its two prime factors are 2 and 3, so a(1) = 5.

%t (* based on the code of _Harvey P. Dale_ in A000396 *)

%t perf=(# (#+1))/2&/@Select[2^Range[1000]-1,PrimeQ];

%t spf[n_]:=Total[First/@FactorInteger[n]];spf/@perf (* _Ivan N. Ianakiev_, Jul 11 2015 *)

%Y Cf. A000396, A008472.

%K nonn

%O 1,1

%A _Madaline McCluskey_, Mar 21 2014

%E Typo in data corrected by _Michel Marcus_, Mar 21 2014

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Last modified December 9 23:02 EST 2019. Contains 329880 sequences. (Running on oeis4.)