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A056240 Smallest number whose prime divisors add to n. 8
2, 3, 4, 5, 8, 7, 15, 14, 21, 11, 35, 13, 33, 26, 39, 17, 65, 19, 51, 38, 57, 23, 95, 46, 69, 92, 115, 29, 161, 31, 87, 62, 93, 124, 155, 37, 217, 74, 111, 41, 185, 43, 123, 86, 129, 47, 215, 94, 141, 188, 235, 53, 329, 106, 159, 212, 265, 59, 371, 61, 177, 122 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

a(n) = index of first occurrence of n in A001414.

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 2..10000

H. Havermann: Tables of sum-of-prime-factors sequences (overview with links to the first 50000 sums).

FORMULA

It appears that this sequence can be computed as follows: if n is prime, a(n) = n. Otherwise, a(n)= (n-k)*a(k) where k is the greatest prime < n-1. - Franklin T. Adams-Watters, Sep 15 2006; corrected by David James Sycamore, Jan 08 2017

EXAMPLE

a(8) = 15 because the smallest number whose prime divisors sum to 8 is 15 (3*5).

MATHEMATICA

a = Table[0, {75}]; Do[b = Plus @@ Flatten[ Table[ #1, {#2}] & @@@ FactorInteger[n]]; If[b < 76 && a[[b]] == 0, a[[b]] = n], {n, 2, 1000}]; a (* Robert G. Wilson v, May 04 2002 *)

PROG

(Haskell)

a056240 = (+ 1) . fromJust . (`elemIndex` a001414_list)

-- Reinhard Zumkeller, Jun 14 2012

CROSSREFS

Cf. A001414, A064502.

First column of array A064364, n>=2.

See A000792 for the maximal numbers whose prime factors sums up to n.

Sequence in context: A074756 A240221 A075162 * A069968 A086931 A243405

Adjacent sequences:  A056237 A056238 A056239 * A056241 A056242 A056243

KEYWORD

nonn,easy

AUTHOR

Adam Kertesz (adamkertesz(AT)worldnet.att.net), Aug 19 2000

EXTENSIONS

More terms from James A. Sellers, Aug 25 2000

STATUS

approved

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Last modified March 27 08:32 EDT 2017. Contains 284146 sequences.