This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A139105 #6 Oct 03 2015 23:14:50 %S A139105 1,1001,1001010111,1001010111010111,1001010111010111010111, %T A139105 100101011101011101011101111101, %U A139105 1001010111010111010111011111010111110111,1001010111010111010111011111010111110111010111,1001010111010111010111011111010111110111010111011111011111,100101011101011101011101111101011111011101011101111101111101011111,100101011101011101011101111101011111011101011101111101111101011111011101,1001010111010111010111011111010111110111010111011111011111010111110111010111110111 %N A139105 Bisection of A139101. %H A139105 Omar E. Pol, <a href="http://polprimos.com">Determinacion geometrica de los numeros primos y perfectos</a>. %F A139105 a(n) = A139101(2n-1). - _R. J. Mathar_, Apr 25 2008 %p A139105 A139101 := proc(n) option remember ; local a,p; if n = 1 then RETURN(1); else a := 10*A139101(n-1) ; for p from ithprime(n-1)+1 to ithprime(n)-1 do a := 10*a+1 ; od: fi ; RETURN(a) ; end: A139105 := proc(n) A139101(2*n-1) ; end: seq(A139105(n),n=1..12) ; # _R. J. Mathar_, Apr 25 2008 %Y A139105 Cf. A139101. %K A139105 base,easy,nonn %O A139105 1,2 %A A139105 _Omar E. Pol_, Apr 08 2008 %E A139105 More terms from _R. J. Mathar_, Apr 25 2008