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A249627 Product of the lowest and highest prime factors of n-th repunit A002275(n). 0
121, 111, 1111, 11111, 111, 1111111, 1507, 1001001, 100001, 11111111111, 29703, 14064697609, 10000001, 8718483, 64705883, 11111111111111111, 1001001, 1234567901234567900987654320987654321, 307571, 32516067, 5645629, 123456790123456790123454320987654320987654321 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

LINKS

Table of n, a(n) for n=2..23.

P. De Geest, Repunits and Their Factors

EXAMPLE

Highest and lowest prime factors of 111111 are 3 and 37, so the sixth term is 111.

PROG

(PARI) for(n=2, 20, p=(10^n-1)/9; print1(factor(p)[1, 1]*factor(p)[#factor(p)[, 1], 1], ", ")) \\ Derek Orr, Nov 02 2014

CROSSREFS

Cf. A002275.

Sequence in context: A197817 A152144 A282344 * A202003 A109838 A014734

Adjacent sequences:  A249624 A249625 A249626 * A249628 A249629 A249630

KEYWORD

nonn,base,easy

AUTHOR

Jacob Vecht, Nov 02 2014

EXTENSIONS

More terms from Derek Orr, Nov 02 2014

STATUS

approved

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Last modified June 19 10:32 EDT 2019. Contains 324219 sequences. (Running on oeis4.)