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 A385609 #12 Jul 16 2025 00:58:45
%S A385609 1,4,5,9,10,13,14,19,20,23,24,28,29,32,33,39,40,43,44,48,49,52,53,58,
%T A385609 59,62,63,67,68,71,72,79,80,83,84,88,89,92,93,98,99,102,103,107,108,
%U A385609 111,112,118,119,122,123,127,128,131,132,137,138,141,142,146,147,150,151
%N A385609 Partial sums of A090740.
%C A385609 Prepended with 0, a trisection of A385608.
%H A385609 Paolo Xausa, <a href="/A385609/b385609.txt">Table of n, a(n) for n = 1..10000</a>
%F A385609 a(n) = Sum_{k=1..n} A090740(k).
%F A385609 a(n) = 2*n + floor(n/2) - A000120(n).
%F A385609 a(n) = A385608(n*3).
%t A385609 A385609[n_] := 2*n + Quotient[n, 2] - DigitSum[n, 2];
%t A385609 Array[A385609, 100] (* or *)
%t A385609 Accumulate[IntegerExponent[3^Range[100] - 1, 2]]
%Y A385609 Cf. A000120, A090740, A385608.
%K A385609 nonn,easy
%O A385609 1,2
%A A385609 _Paolo Xausa_, Jul 04 2025