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A103182 Sliding numbers: numbers n of the form n = r+s where 1/r + 1/s = (r+s)/10^k for some k >= 1. 2
2, 7, 11, 20, 25, 29, 52, 65, 70, 101, 110, 133, 200, 205, 205, 250, 254, 290, 425, 502, 520, 641, 650, 700, 785, 925, 1001, 1010, 1100, 1258, 1330, 2000, 2005, 2050, 2050, 2225, 2500, 2504, 2540, 2900, 3157, 3445, 4025, 4250, 5002, 5020 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Note that 1/20 + 1/50 = 0.70 --> 70 is a "sliding number" though 0.70 is usually written 0.7 So any "sliding number" G produces an infinite chain of others : G*10, G*100, G*1000, etc. The first number in such a chain is called "primitive".

Another characterization of the sliding numbers is numbers of the form a + 10^k/a where a | 10^k (k >= 0). - David W. Wilson, Mar 09 2005

The left-hand side is (a+b)/ab and we can cancel out (a+b), so we are looking for all (a+b) with a and b positive integers, such that a*b is a (nonnegative integral) power of 10, sorted by (a+b). It follows for example that for a given k, the smallest (a+b) with that k is 2*sqrt(10^k) (equality when k i even, unless we also require a!=b). - Chris Landauer (cal(AT)rushg.aero.org), Mar 10 2005

LINKS

Table of n, a(n) for n=1..46.

EXAMPLE

1/4 + 1/25 = 0.29 --> 29 is a "sliding number"

1/8 + 1/125 = 0.133 --> 133 is a "sliding number"

1/2 + 1/5 = 0.7 --> 7 is a "sliding number"

CROSSREFS

Cf. A103183, A103184.

Sequence in context: A139603 A141183 A308724 * A160698 A294114 A144707

Adjacent sequences:  A103179 A103180 A103181 * A103183 A103184 A103185

KEYWORD

nonn

AUTHOR

Eric Angelini, Mar 09 2005

EXTENSIONS

More terms from Kerry Mitchell, Mar 09 2005

STATUS

approved

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Last modified February 17 00:25 EST 2020. Contains 331976 sequences. (Running on oeis4.)