

A124244


a(n) is the smallest odd prime p such that 2^n*p has n digits but has at most two distinct digits; or 0 if no such prime exists.


1



3, 3, 29, 101, 691, 15467, 39023, 71023, 437977, 4344227, 21158903, 109739989, 344590189, 2956838897, 6781690193, 0, 85533990571, 3390460543777, 0, 53936545044581, 0, 0, 5298071316879193, 0, 168548719780643483
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OFFSET

1,1


COMMENTS

Andrew Rupinski showed that a(95) exists (see the links below).


LINKS



EXAMPLE

a(14)=2956838897 because 2^14*2956838897=48444848488448 has 14 digits with two distinct digits and 2956838897 is the smallest prime p such that 2^14*p has these properties.


MATHEMATICA

a[1]=3; a[n_]:=(For[m=Floor[5^(n1)/2], !(PrimeQ[m]&&Length[Union[ IntegerDigits[2^n*m]]]==2&&Length[IntegerDigits[2^n*m]]==n), m++ ]; m); Do[Print[a[n]], {n, 14}]


CROSSREFS



KEYWORD

nonn,base


AUTHOR



EXTENSIONS



STATUS

approved



