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A112722 First n-digit number m such that sigma(m) is prime. 0
2, 16, 289, 1681, 10201, 146689, 1190281, 10374841, 103042801, 1023424081, 10009802401, 100019755081, 1000242014641, 10001235475729, 100001580006241, 1000017101564209, 10000044600049729, 100000569832596889 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Each term is of the form p^k where p is prime. For n > 1, k is even.

Can it be proved that a(n) exists for all n?

LINKS

Table of n, a(n) for n=1..18.

CROSSREFS

Sequence in context: A254744 A009795 A182562 * A223664 A189611 A189689

Adjacent sequences:  A112719 A112720 A112721 * A112723 A112724 A112725

KEYWORD

nonn,base

AUTHOR

Farideh Firoozbakht, Oct 10 2005

STATUS

approved

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Last modified August 11 03:41 EDT 2022. Contains 356046 sequences. (Running on oeis4.)