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A125521 a(n) = minimal difference between two distinct n-digit numbers with property that when one of them is typed into a calculator and rotated 180 degrees, the other one is seen. 0
3, 6, 30, 60, 300, 600, 3000, 6000, 30000, 60000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..10.

FORMULA

If n is even, a(n) is 6 followed by (n - 2) / 2 zeros. If n is odd, a(n) is 3 followed by (n - 1) / 2 zeros.

EXAMPLE

a(3) = 30. If one types 595 into a calculator and rotates it 180 degrees, they will get 565. 595 - 565 = 30. With a little thought, it is provable that 30 is the smallest possible difference.

CROSSREFS

Sequence in context: A136939 A136944 A136946 * A211168 A215294 A090932

Adjacent sequences:  A125518 A125519 A125520 * A125522 A125523 A125524

KEYWORD

base,nonn

AUTHOR

Tanya Khovanova and Sergei Bernstein, Dec 29 2006

STATUS

approved

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Last modified March 29 12:56 EDT 2017. Contains 284270 sequences.