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Numbers k such that the sum of the first k terms of A180405 is composite.
3

%I #22 Jun 07 2023 11:02:33

%S 5,9,13,17,21,25,27,33,41,47,55,61,65,69,75,83,89,95,105,107,113,119,

%T 125,128,133,139,145,155,161,165,171,179,183,189,197,201,207,211,217,

%U 225,231,237,241,247,255,261,267,271,279,285,289,297,303,307,313,319,327,333,339,343,351

%N Numbers k such that the sum of the first k terms of A180405 is composite.

%C The construction in A180405 means terms here cannot be terms there, but do any other numbers never occur there?

%C Indices of composite terms in A363450 (partial sums of A180405).

%C a(24)=128 is possibly the only even term in the sequence (checked for 6000 terms).

%H Neal Gersh Tolunsky, <a href="/A363379/b363379.txt">Table of n, a(n) for n = 1..6098</a>

%Y Cf. A180405, A363450.

%K nonn,easy

%O 1,1

%A _Neal Gersh Tolunsky_, May 29 2023