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%I #8 Feb 18 2019 02:31:09
%S 149,1009,10009,100049,1000849,10000169,100000891,1000000009,
%T 10000001041,100000000669,1000000000091,10000000001011,
%U 100000000000469,1000000000004449,10000000000001101,100000000000000049
%N Smallest n-digit emirp with only nonprime digits.
%C 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.
%e 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.
%p isA084984 := proc(n) convert(convert(n,base,10),set) ; if % intersect {2,3,5,7} = {} then true; else false; end if; end proc:
%p 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:
%p seq(A177850(n),n=3..40) ; # _R. J. Mathar_, May 24 2010
%Y Cf. A000040, A004086, A006567, A034844, A128390, A177513.
%K base,easy,nonn
%O 3,1
%A _Jonathan Vos Post_, May 14 2010
%E More terms from _R. J. Mathar_, May 24 2010
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