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 A087077 #16 Feb 16 2025 08:32:50
%S A087077 0,1,2,5,8,21,29,73,105,193,288,677,853,1957,2961,4913,6809,15145,
%T A087077 19605,43105,57889,98849,151457,327505,397825,784945,1201189,2009229,
%U A087077 2772729,5901185,7364945,15609825,21206049,36440033,55602033,105010513,127336513,267374561
%N A087077 Total number of elements in all primitive subsets of the integers 1 to n.
%C A087077 A primitive set has no element that divides another element in the same set.
%D A087077 R. K. Guy, Unsolved Problems in Number Theory, Springer-Verlag, New York, (1994).
%H A087077 Fausto A. C. Cariboni, <a href="/A087077/b087077.txt">Table of n, a(n) for n = 0..75</a>
%H A087077 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/PrimitiveSequence.html">Primitive Sequence</a>.
%F A087077 a(n) = Sum_{k=1..ceiling(n/2)} k * A355145(n,k). - _Alois P. Heinz_, Jun 27 2022
%e A087077 a(4)=8 since the primitive subsets of (1,2,3,4) are ( ) (1) (2) (3) (4) (2,3) (3,4) and these contain eight elements
%Y A087077 A051026 gives the number of primitive subsets. A087078 gives the sum of the elements of the primitive subsets. A087080 gives the number elements in the coprime subsets.
%Y A087077 Cf. A355145.
%K A087077 nonn
%O A087077 0,3
%A A087077 Alan Sutcliffe (alansut(AT)ntlworld.com), Aug 10 2003
%E A087077 Terms a(34)-a(37) from _Fausto A. C. Cariboni_, Feb 02 2022