A177850 Smallest n-digit emirp with only nonprime digits.

149, 1009, 10009, 100049, 1000849, 10000169, 100000891, 1000000009, 10000001041, 100000000669, 1000000000091, 10000000001011, 100000000000469, 1000000000004449, 10000000000001101, 100000000000000049

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