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 A349304 #18 Dec 27 2021 14:59:11
%S A349304 1,3,13,63,1641,55979,1963261,1051838303,427823653777,899765549835411,
%T A349304 962612860717614517,16451240378526759988983,
%U A349304 275851420933163891499583577,75079775107059278497058879826395,1275913767034795679914048924532788093,1386272923043819758818080175342943182028095
%N A349304 Terms of sequence A133342 interpreted as numbers written in base 2 and converted here to base 10.
%C A349304 a(n) is a Mersenne number (A000225) iff n = 0, 1, 3 (see proof in A133342).
%t A349304 a[n_] := FromDigits[Join @@ Table[IntegerDigits[Binomial[n, k], 2], {k, 0, n}], 2]; Array[a, 15, 0] (* _Amiram Eldar_, Nov 14 2021 *)
%o A349304 (PARI) a(n) = fromdigits(concat(vector(n+1, k, binary(binomial(n, k-1)))), 2); \\ _Michel Marcus_, Nov 14 2021
%Y A349304 Cf. A000225, A003590, A007318, A133342.
%K A349304 nonn,base
%O A349304 0,2
%A A349304 _Bernard Schott_, Nov 14 2021