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 A131700 #12 Feb 16 2025 08:33:06
%S A131700 13,90,1443,6658,81923,827395,17956868,157286403,1434451971,
%T A131700 12884901891,114353504259,1005022347267,8761733283843,166026255794180,
%U A131700 1337006139375619,11434920928870403,97390341941886979,1799188051134513156,14231374822490767363,119903836479112085507
%N A131700 Sum of all n-digit Cullen numbers.
%H A131700 E.W. Weisstein, <a href="https://mathworld.wolfram.com/CullenNumber.html">Cullen Number</a>
%e A131700 Sum of all 1-digit Cullen numbers is 1 + 3 + 9 = 13.
%e A131700 Sum of all 2-digit Cullen numbers is 25 + 65 = 90.
%e A131700 Sum of all 3-digit Cullen numbers is 161 + 385 + 897 = 1443.
%t A131700 digNum[n_] := Length @ IntegerDigits[n]; cullen[n_] := n * 2^n + 1; digCount = 0; sum = 0; cumsum = {}; Do[c = cullen[n]; If[digNum[c] > digCount, digCount++; AppendTo[cumsum, sum]]; sum += c, {n, 0, 65}]; Differences[cumsum] (* _Amiram Eldar_, Nov 30 2019 *)
%Y A131700 Cf. A002064.
%K A131700 nonn,base,less
%O A131700 1,1
%A A131700 _Parthasarathy Nambi_, Sep 15 2007
%E A131700 More terms from _Amiram Eldar_, Nov 30 2019