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# Ruth–Aaron pair

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 Title: Ruth–Aaron pair Author: World Heritage Encyclopedia Language: English Subject: Collection: Publisher: World Heritage Encyclopedia Publication Date:

### Ruth–Aaron pair

In mathematics, a Ruth–Aaron pair consists of two consecutive integers (e.g. 714 and 715) for which the sums of the prime factors of each integer are equal:

714 = 2 × 3 × 7 × 17
715 = 5 × 11 × 13

and

2 + 3 + 7 + 17 = 5 + 11 + 13 = 29

If only distinct prime factors are counted, the first few Ruth–Aaron pairs are:

(5, 6), (24, 25), (49, 50), (77, 78), (104, 105), (153, 154), (369, 370), (492, 493), (714, 715), (1682, 1683), (2107, 2108)

(The lesser of each pair is listed in (sequence A006145 in OEIS)).

Counting repeated prime factors (e.g. 8 = 2×2×2 and 9 = 3×3 with 2+2+2 = 3+3), the first few Ruth–Aaron pairs are:

(5, 6), (8, 9), (15, 16), (77, 78), (125, 126), (714, 715), (948, 949), (1330, 1331)

(The lesser of each pair is listed in  A039752).

The intersection of the two lists begins:

(5, 6), (77, 78), (714, 715), (5405, 5406)

(The lesser of each pair is listed in  A039753).

Any Ruth–Aaron pair of square-free integers belongs to both lists with the same sum of prime factors. The intersection also contains pairs that are not square-free, for example (7129199, 7129200) = (7×112×19×443, 24×3×52×13×457). Here 7+11+19+443 = 2+3+5+13+457 = 480, and also 7+11+11+19+443 = 2+2+2+2+3+5+5+13+457 = 491.

The name was given by Atlanta Braves) broke Ruth's record, and the student of one of Pomerance's colleagues noticed that the sums of the prime factors of 714 and 715 were equal.

## Ruth–Aaron triplets

Ruth–Aaron triplets (overlapping Ruth–Aaron pairs) also exist. The first and possibly the second when counting distinct prime factors:

89460294 = 2 × 3 × 7 × 11 × 23 × 8419
89460295 = 5 × 4201 × 4259
89460296 = 2 × 2 × 2 × 31 × 43 × 8389
and 2 + 3 + 7 + 11 + 23 + 8419 = 5 + 4201 + 4259 = 2 + 31 + 43 + 8389 = 8465
151165960539 = 3 × 11 × 11 × 83 × 2081 × 2411
151165960540 = 2 × 2 × 5 × 7 × 293 × 1193 × 3089
151165960541 = 23 × 29 × 157 × 359 × 4021
and 3 + 11 + 83 + 2081 + 2411 = 2 + 5 + 7 + 293 + 1193 + 3089 = 23 + 29 + 157 + 359 + 4021 = 4589

The first two Ruth–Aaron triplets when counting repeated prime factors:

417162 = 2 × 3 × 251 × 277
417163 = 17 × 53 × 463
417164 = 2 × 2 × 11 × 19 × 499
and 2 + 3 + 251 + 277 = 17 + 53 + 463 = 2 + 2 + 11 + 19 + 499 = 533
6913943284 = 2 × 2 × 37 × 89 × 101 × 5197
6913943285 = 5 × 283 × 1259 × 3881
6913943286 = 2 × 3 × 167 × 2549 × 2707
and 2 + 2 + 37 + 89 + 101 + 5197 = 5 + 283 + 1259 + 3881 = 2 + 3 + 167 + 2549 + 2707 = 5428

As of 2006 only the 4 above triplets are known.