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A108903 Numbers such that the outer 2 digits are 9 and the inner digits are 5. 0
959, 9559, 95559, 955559, 9555559, 95555559, 955555559, 9555555559, 95555555559, 955555555559, 9555555555559, 95555555555559, 955555555555559, 9555555555555559, 95555555555555559, 955555555555555559 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

These numbers are all composite. They are divisible among other numbers by 3,7,11,13 depending on the form 6k+r, 0 < r < 6. See the link for a proof.

LINKS

Table of n, a(n) for n=1..16.

Cino Hilliard, Proof 955..559 is composite.

FORMULA

S(x)=9*10^(x+1)+ 9 + 50*(10^x-1)/9.

PROG

(PARI) g(n, r, m) = epeat rrr.. surrounded by 2 m's { for(x=1, n, y=m*10^(x+1)+m+r*10*(10^x-1)/9; print(x", ") ) }

CROSSREFS

Sequence in context: A031903 A226851 A158410 * A167780 A316338 A257417

Adjacent sequences:  A108900 A108901 A108902 * A108904 A108905 A108906

KEYWORD

easy,nonn,base

AUTHOR

Cino Hilliard, Jul 16 2005

STATUS

approved

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Last modified August 13 19:30 EDT 2020. Contains 336451 sequences. (Running on oeis4.)