A077805 - OEIS

%I #7 Feb 06 2019 17:19:05

%S 1,2,11,2,101,2,3,2,7,2,3,2,3,2,11,2,73,2,3,2,3,2,10111,2,3,2,7,2,17,

%T 2,41,2,11,2,3,2,3,2,11,2,3,2,83,2,7,2,101111,2,3,2,11,2,23,2,149,2,

%U 11,2,31,2,241,2,3,2,101,2,3,2,3,2,7,2,3,2,11,2,971,2,181,2,3,2,31,2,73,2

%N Smallest prime factor of numbers containing in their decimal representation only the digits 0 and 1.

%H Antti Karttunen, <a href="/A077805/b077805.txt">Table of n, a(n) for n = 1..16384</a>

%F a(n) = A020639(A007088(n)).

%e a(45) = A020639(A007088(45)) = A020639(101101) = A020639(7*11*13*101) = 7.

%o (PARI)

%o A007088(n) = fromdigits(binary(n), 10); \\ From A007088.

%o A020639(n) = if(1==n, n, factor(n)[1, 1]);

%o A077805(n) = A020639(A007088(n)); \\ _Antti Karttunen_, Feb 06 2019

%Y Cf. A007088, A020639, A077806, A020449.

%K nonn,base

%O 1,2

%A _Reinhard Zumkeller_, Nov 16 2002