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A177850 Smallest n-digit emirp with only nonprime digits. 1
149, 1009, 10009, 100049, 1000849, 10000169, 100000891, 1000000009, 10000001041, 100000000669, 1000000000091, 10000000001011, 100000000000469, 1000000000004449, 10000000000001101, 100000000000000049 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

Least value of emirps with only nonprime digits (i.e., 0,1,4,6,8,9) A128390, with n digits. This is to primes with nonprime digits (A034844) as smallest n-digit emirp with only prime digits (A177513) is to primes with only prime digits.

LINKS

Table of n, a(n) for n=3..18.

EXAMPLE

a(6) = 100049 because all digits {0,1,4,9} are nonprime, and 100049 is prime, and R(100049) = A004086(100049) = 940001 is prime, and there is no smaller 6-digit number meeting these criteria.

MAPLE

isA084984 := proc(n) convert(convert(n, base, 10), set) ; if % intersect {2, 3, 5, 7} = {} then true; else false; end if; end proc:

A177850 := proc(n) local a; a := 10^(n-1) ; while not (isA006567(a) and isA084984(a)) do a := nextprime(a) ; end do; if a < 10^n then return a ; else return -1 ; end if; end proc:

seq(A177850(n), n=3..40) ; # R. J. Mathar, May 24 2010

CROSSREFS

Cf. A000040, A004086, A006567, A034844, A128390, A177513.

Sequence in context: A078950 A251313 A142269 * A158717 A243530 A219081

Adjacent sequences:  A177847 A177848 A177849 * A177851 A177852 A177853

KEYWORD

base,easy,nonn

AUTHOR

Jonathan Vos Post, May 14 2010

EXTENSIONS

More terms from R. J. Mathar, May 24 2010

STATUS

approved

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Last modified February 21 02:02 EST 2020. Contains 332086 sequences. (Running on oeis4.)