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 A293522 #17 Mar 14 2025 07:04:48
%S A293522 1,1,2,2,3,5,5,5,9,12,17,21,27,36,50,64,89,114,156,201,261,353,480,
%T A293522 639,870,1163,1562,2116,2826,3798,5080,6884,9176,12329,16627,22262,
%U A293522 29980,40421,54126,72642,97877,131266,176638,237227,318659,427624,574993,772511,1038418,1395802
%N A293522 Number of bifurcating nodes at generation n in the binary tree of persistently squarefree numbers (see A293230).
%C A293522 Bifurcating node is one that branches to two alive nodes in the next generation (level) of the tree.
%F A293522 a(n) = Sum_{k=(2^n)..(2^(1+n)-1)} abs(A293233(k)) * A008966(2*k) * A008966(1+2*k).
%F A293522 a(n) <= A293441(n). [Because no even node can bifurcate.]
%e A293522 a(2) = 2 because in the binary tree illustrated in A293230, there are two nodes at the level 2 (namely 5 and 7) that spawn two offspring each.
%o A293522 (PARI) \\ See program at A293520.
%Y A293522 Cf. A293230, A293441, A293520, A293521.
%K A293522 nonn
%O A293522 0,3
%A A293522 _Antti Karttunen_, Oct 12 2017