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A008472
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Sum of the distinct primes dividing n.
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271
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0, 2, 3, 2, 5, 5, 7, 2, 3, 7, 11, 5, 13, 9, 8, 2, 17, 5, 19, 7, 10, 13, 23, 5, 5, 15, 3, 9, 29, 10, 31, 2, 14, 19, 12, 5, 37, 21, 16, 7, 41, 12, 43, 13, 8, 25, 47, 5, 7, 7, 20, 15, 53, 5, 16, 9, 22, 31, 59, 10, 61, 33, 10, 2, 18, 16, 67, 19, 26, 14, 71, 5, 73
(list;
graph;
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listen;
history;
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OFFSET
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1,2
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COMMENTS
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Sometimes called sopf(n).
Sum of primes dividing n (without repetition) (compare A001414).
Equals A051731 * A061397 = inverse Mobius transform of [0, 2, 3, 0, 5, 0, 7, ...]. - Gary W. Adamson, Feb 14 2008
Equals row sums of triangle A143535. - Gary W. Adamson, Aug 23 2008
a(n) = n if and only if n is prime. - Daniel Forgues, Mar 24 2009
a(n) = n is a new record if and only if n is prime. - Zak Seidov, Jun 27 2009
a(A001043(n)) = A191583(n);
For n > 0: a(A000079(n)) = 2, a(A000244(n)) = 3, a(A000351(n)) = 5, a(A000420(n)) = 7;
a(A006899(n)) <= 3; a(A003586(n)) = 5; a(A033846(n)) = 7; a(A033849(n)) = 8; a(A033847(n)) = 9; a(A033850(n)) = 10; a(A143207(n)) = 10. - Reinhard Zumkeller, Jun 28 2011
For n > 1: a(n) = Sum(A027748(n,k): 1 <= k <= A001221(n)). - Reinhard Zumkeller, Aug 27 2011
If n is the product of twin primes (A037074), a(n) = 2*sqrt(n+1) = sqrt(4n+4). - Wesley Ivan Hurt, Sep 07 2013
From Wilf A. Wilson, Jul 21 2017: (Start)
a(n) + 2, n > 2, is the number of maximal subsemigroups of the monoid of orientation-preserving or -reversing mappings on a set with n elements.
a(n) + 3, n > 2, is the number of maximal subsemigroups of the monoid of orientation-preserving or -reversing partial mappings on a set with n elements.
(End)
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LINKS
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Franklin T. Adams-Watters and Daniel Forgues, Table of n, a(n) for n = 1..100000 (first 10000 terms from Franklin T. Adams-Watters)
Johann Bartel, R. K. Bhaduri, Matthias Brack, M. V. N. Murthy, On the asymptotic prime partitions of integers, arXiv:1609.06497 [math-ph], 2017.
James East, Jitender Kumar, James D. Mitchell, and Wilf A. Wilson, Maximal subsemigroups of finite transformation and partition monoids, arXiv:1706.04967 [math.GR], 2017. [Wilf A. Wilson, Jul 21 2017]
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FORMULA
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Let n = Product_j prime(j)^k(j) where k(j)>=1, then a(n) = Sum_j prime(j).
Additive with a(p^e) = p.
G.f.: sum(k >= 1, prime(k)*x^prime(k)/(1-x^prime(k))). - Franklin T. Adams-Watters, Sep 01 2009
L.g.f.: -log(Product_{k>=1} (1 - x^prime(k))) = Sum_{n>=1} a(n)*x^n/n. - Ilya Gutkovskiy, May 06 2017
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EXAMPLE
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a(18) = 5 because 18 = 2 * 3^2 and 2 + 3 = 5.
a(19) = 19 because 19 is prime.
a(20) = 7 because 20 = 2^2 * 5 and 2 + 5 = 7.
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MAPLE
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A008472 := n -> add(d, d = select(isprime, numtheory[divisors](n))):
seq(A008472(i), i = 1..40); # Peter Luschny, Jan 31 2012
A008472 := proc(n)
add( d, d= numtheory[factorset](n)) ;
end proc: # R. J. Mathar, Jul 08 2012
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MATHEMATICA
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Prepend[Array[Plus @@ First[Transpose[FactorInteger[#]]] &, 100, 2], 0]
Join[{0}, Rest[Total[Transpose[FactorInteger[#]][[1]]]&/@Range[100]]] (* Harvey P. Dale, Jun 18 2012 *)
(* Requires version 7.0+ *) Table[DivisorSum[n, # &, PrimeQ[#] &], {n, 75}] (* Alonso del Arte, Dec 13 2014 *)
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PROG
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(PARI) sopf(n) = local(fac=factor(n)); sum(i=1, matsize(fac)[1], fac[i, 1])
(PARI) vector(100, n, vecsum(factor(n)[, 1]~)) \\ Derek Orr, May 13 2015
(PARI) A008472(n)=vecsum(factor(n)[, 1]) \\ M. F. Hasler, Jul 18 2015
(Sage)
def A008472(n) :
D = filter(is_prime, divisors(n))
return add(d for d in D)
print [A008472(i) for i in (1..40)] # Peter Luschny, Jan 31 2012
(Sage) [sum(prime_factors(n)) for n in range(1, 74)] # Giuseppe Coppoletta, Jan 19 2015
(Haskell)
a008472 = sum . a027748_row -- Reinhard Zumkeller, Mar 29 2012
(MAGMA) [n eq 1 select 0 else &+[p[1]: p in Factorization(n)]: n in [1..100]]; // Vincenzo Librandi, Jun 24 2017
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CROSSREFS
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First difference of A024924.
Cf. A001414 (sopfr), A001222, A051731, A061397, A143535, A085020.
Sequence in context: A095402 A086294 A075860 * A123528 A074036 A074251
Adjacent sequences: A008469 A008470 A008471 * A008473 A008474 A008475
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KEYWORD
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nonn,nice,easy
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AUTHOR
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Olivier Gérard
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STATUS
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approved
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