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 A246649 #7 Feb 05 2019 16:00:37
%S A246649 1,1,17,1334440654591915542993625911497130241,
%T A246649 948042080603099421350928003060030968743284199473954197137709371401
%N A246649 Integers of the form (2^(k+1) - 1)/(2*k + 1).
%C A246649 The next term has 192 digits. - _Harvey P. Dale_, Feb 05 2019
%e A246649 The sum of the numbers row 7 of the triangular array at A027926 is 2^8 - 1 = 255, and the number of numbers in row 7 is 15, and 255/15 = 17; thus 7 is in this sequence, and 17 is in A246649.
%t A246649 z = 140000; u = Select[Range[0, z], IntegerQ[(2^(# + 1) - 1)/(2 # + 1)] &] (* A246648 *)
%t A246649 v = Table[(2^(u[[k]] + 1) - 1)/(2 u[[k]] + 1), {k, 1, 6}] (* A246649 *)
%t A246649 Select[Table[(2^(n+1)-1)/(2n+1),{n,0,250}],IntegerQ] (* _Harvey P. Dale_, Feb 05 2019 *)
%Y A246649 Cf. A246637, A246648.
%K A246649 nonn,easy
%O A246649 1,3
%A A246649 _Clark Kimberling_, Sep 01 2014