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A001414 Integer log of n: sum of primes dividing n (with repetition).
(Formerly M0461 N0168)
277
0, 2, 3, 4, 5, 5, 7, 6, 6, 7, 11, 7, 13, 9, 8, 8, 17, 8, 19, 9, 10, 13, 23, 9, 10, 15, 9, 11, 29, 10, 31, 10, 14, 19, 12, 10, 37, 21, 16, 11, 41, 12, 43, 15, 11, 25, 47, 11, 14, 12, 20, 17, 53, 11, 16, 13, 22, 31, 59, 12, 61, 33, 13, 12, 18, 16, 67, 21, 26, 14, 71, 12, 73, 39, 13, 23, 18, 18 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

MacMahon calls this the potency of n.

Sometimes also called sopfr(n).

Downgrades the operators in a prime decomposition. E.g., 40 factors as 2^3 * 5 and sopfr(40) = 2 * 3 + 5 = 11.

Consider all ways of writing n as a product of zero, one, or more factors; sequence gives smallest sum of terms. - Amarnath Murthy, Jul 07 2001

a(n) <= n for all n, and a(n) = n iff n is 4 or a prime.

Look at the graph of this sequence. At the lower edge of the logarithmic scatterplot there is a set of fuzzy but unmistakable diagonal fringes, sloping toward the southeast. Their spacing gradually increases, and their slopes gradually decrease; they are more distinct toward the lower edge of the range. Is any explanation known? - Allan C. Wechsler, Oct 11 2015

For n >= 2, the glb and lub are: 3 * log(n) / log(3) <= a(n) <= n, where the lub occurs when n = 3^k, k >= 1. (Jakimczuk 2012) - Daniel Forgues, Oct 12 2015

Except for the initial term, row sums of A027746. - M. F. Hasler, Feb 08 2016

Atanassov proves that a(n) <= A065387(n) - n. - Charles R Greathouse IV, Dec 06 2016

REFERENCES

K. Atanassov, New integer functions, related to ψ and σ functions. IV., Bull. Number Theory Related Topics 12 (1988), pp. 31-35.

Amarnath Murthy, Generalization of Partition function and introducing Smarandache Factor Partition, Smarandache Notions Journal, Vol. 11, 1-2-3, Spring-2000.

Amarnath Murthy and Charles Ashbacher, Generalized Partitions and Some New Ideas on Number Theory and Smarandache Sequences, Hexis, Phoenix; USA 2005. See Section 1.4.

J. Roberts, Lure of the Integers, Math. Assoc. America, 1992, p. 89.

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Franklin T. Adams-Watters and Daniel Forgues, Table of n, a(n) for n = 1..100000 (first 10000 terms from Franklin T. Adams-Watters)

K. Alladi and P. Erdős, On an additive arithmetic function, Pacific J. Math., Volume 71, Number 2 (1977), 275-294.

K. S. Brown, The Sum of the Prime Factors of N

Hans Havermann, Log plot of 100000 terms

J. Iraids, K. Balodis, J. Cernenoks, M. Opmanis, R. Opmanis and K. Podnieks, Integer Complexity: Experimental and Analytical Results. arXiv preprint arXiv:1203.6462 [math.NT], 2012.

Rafael Jakimczuk, Sum of Prime Factors in the Prime Factorization of an Integer, International Mathematical Forum, Vol. 7, 2012, no. 53, 2617 - 2621.

M. Lal, Iterates of a number-theoretic function, Math. Comp., 23 (1969), 181-183.

P. A. MacMahon, Properties of prime numbers deduced from the calculus of symmetric functions, Proc. London Math. Soc., 23 (1923), 290-316. = Coll. Papers, II, pp. 354-380.

Eric Weisstein's World of Mathematics, Sum of Prime Factors

Wikipedia, Table of prime factors

FORMULA

If n = Product (p_j^k_j) then a(n) = Sum (p_j * k_j).

Dirichlet g.f. f(s)*zeta(s), where f(s) = sum_{p prime} p/(p^s-1) = sum_{k>0} primezeta(k*s-1) is the Dirichlet g.f. for A120007. Totally additive with a(p^e) = p*e. - Franklin T. Adams-Watters, Jun 02 2006

For n > 1: a(n) = sum(k=1..A001222(n), A027746(n,k)). - Reinhard Zumkeller, Aug 27 2011

EXAMPLE

a(24) = 2+2+2+3 = 9.

a(30) = 10: 30 can be written as 30, 15*2, 10*3, 6*5, 5*3*2. The corresponding sums are 30, 17, 13, 11, 10. Among these 10 is the least.

MAPLE

A001414 := proc(n) local e, j; e := ifactors(n)[2]: add(e[j][1]*e[j][2], j=1..nops(e)) end:

seq(A001414(n), n=1..100); # Peter Luschny, Jan 17 2011

MATHEMATICA

f[n_] := Plus @@ Times @@@ FactorInteger@ n; f[1] = 0; Array[f, 78] (* Ray Chandler, Nov 12 2005 *)

PROG

(PARI) a(n)=local(f); if(n<1, 0, f=factor(n); sum(k=1, matsize(f)[1], f[k, 1]*f[k, 2]))

(PARI) A001414(n) = (n=factor(n))[, 1]~*n[, 2] \\ M. F. Hasler, Feb 07 2009

(Haskell)

a001414 1 = 0

a001414 n = sum $ a027746_row n

-- Reinhard Zumkeller, Feb 27 2012, Nov 20 2011

(Sage) [sum(factor(n)[j][0]*factor(n)[j][1] for j in range(0, len(factor(n)))) for n in range(1, 79)] # Giuseppe Coppoletta, Jan 19 2015

(Python)

from sympy import factorint

def A001414(n):

    return sum(p*e for p, e in factorint(n).items()) # Chai Wah Wu, Jan 08 2016

CROSSREFS

Cf. A008472 (sopf(n)), A002217, A056240, A000792, A046343, A120007, A036288.

A000607(n) gives the number of values of k for which A001414(k) = n.

For sum of squares of primes see A067666, for cubes see A224787.

Sequence in context: A086295 A159303 A262049 * A134875 A134889 A181894

Adjacent sequences:  A001411 A001412 A001413 * A001415 A001416 A001417

KEYWORD

nonn,easy,nice,changed

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified December 10 21:05 EST 2016. Contains 279011 sequences.