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 A261067 #24 Sep 08 2022 08:46:13
%S A261067 15,915,6698715,717964529118315,16495138082306681918325119173515,
%T A261067 17413733142679306233865281770975943513633443105435651232476307915
%N A261067 a(n) = (11^(2^n) - 1)/2^(n + 2).
%C A261067 (m^(2^n) - 1)/2^(n + 2) is an integer for any odd value of m and n > 0.
%C A261067 In particular, for m = 11, a(n) is a multiple of 15.
%F A261067 a(n) = 15*A068533(n). - _Michel Marcus_, Aug 14 2015
%e A261067 a(3) = (11^8 - 1)/2^5 = 6698715.
%p A261067 A261067:=n->(11^(2^n) - 1)/2^(n + 2): seq(A261067(n), n=1..8); # _Wesley Ivan Hurt_, Jan 27 2017
%t A261067 Table[(11^(2^n) - 1)/2^(n + 2), {n, 10}] (* _Vincenzo Librandi_, Aug 14 2015 *)
%o A261067 (PARI) first(m)=vector(m,i, (11^(2^i)-1)/2^(i+2)); /* _Anders Hellström_, Aug 08 2015 */
%o A261067 (Magma) [(11^(2^n)-1)/2^(n+2): n in [1..6]]; // _Vincenzo Librandi_, Aug 14 2015
%Y A261067 Cf. A059723, A068531, A068533, A097421.
%K A261067 nonn,easy
%O A261067 1,1
%A A261067 _Marco Ripà_, Aug 08 2015