OFFSET
1,3
COMMENTS
Primes counted without multiplicity. - Harvey P. Dale, Aug 28 2019
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
FORMULA
Additive with a(p^e) = 0 if p = 2, p otherwise.
G.f.: Sum_{k>=2} prime(k)*x^prime(k)/(1 - x^prime(k)). - Ilya Gutkovskiy, Dec 24 2016
From Antti Karttunen, Jul 10 & 11 2017: (Start)
(End)
MATHEMATICA
a = {0, 0}; For[n = 3, n < 80, n++, su = 0; b = FactorInteger[n]; For[i = 1, i < Length[b] + 1, i++, If[OddQ[b[[i, 1]]], su = su + b[[i, 1]]]]; AppendTo[a, su]]; a (* Stefan Steinerberger, Jun 02 2007 *)
Array[DivisorSum[#, # &, And[PrimeQ@ #, OddQ@ #] &] &, 79] (* Michael De Vlieger, Jul 11 2017 *)
Join[{0}, Table[Total[FactorInteger[n][[All, 1]]/.(2->0)], {n, 2, 100}]] (* Harvey P. Dale, Aug 28 2019 *)
PROG
(Scheme) (define (A005069 n) (cond ((= 1 n) 0) ((even? n) (A005069 (/ n 2))) (else (+ (A020639 n) (A005069 (A028234 n)))))) ;; Antti Karttunen, Jul 10 2017
(PARI) a(n) = my(f=factor(n)); sum(k=1, #f~, if (((p=f[k, 1])%2) == 1, p)); \\ Michel Marcus, Jul 11 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
More terms from Stefan Steinerberger, Jun 02 2007
STATUS
approved