A088115 - OEIS

A088115

a(n) = largest prime using least number of possible digits with a digit sum n, or 0 if no such number exists. E.g., if n > 9 and there are no two-digit primes with a given digit sum n then three-digit numbers are explored and so on.

0, 2, 3, 31, 5, 0, 7, 71, 0, 73, 83, 0, 67, 59, 0, 97, 89, 0, 991, 983, 0, 967, 977, 0, 997, 9791, 0, 9973, 9929, 0, 9967, 9887, 0, 99961, 8999, 0, 99991, 99929, 0, 99877, 99689, 0, 98899, 99989, 0, 999883, 999983, 0, 999769, 999959, 0, 999979, 989999, 0

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OFFSET

1,2

COMMENTS

a(26) = 9719 as both 989 and 899 are composite. This is the first genuine case in which the number of digits used is more than floor(n/9) + 1 (after single-digit composite even numbers 4 and 8).

LINKS

Table of n, a(n) for n=1..54.

EXAMPLE

a(7) = 7.

a(8) = 71 as 8 is not a prime.

CROSSREFS

Sequence in context: A326224 A270483 A217370 * A230627 A048986 A093712

Adjacent sequences: A088112 A088113 A088114 * A088116 A088117 A088118

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Sep 25 2003

EXTENSIONS

More terms from David Wasserman, Jul 25 2005

STATUS

approved