A293521 Number of surviving (but not bifurcating) nodes at generation n in the binary tree of persistently squarefree numbers (see A293230).

0, 1, 1, 3, 3, 2, 5, 9, 8, 11, 15, 24, 30, 42, 51, 76, 94, 126, 158, 217, 298, 403, 539, 731, 970, 1305, 1748, 2322, 3179, 4225, 5715, 7596, 10259, 13731, 18357, 24771, 33184, 44448, 59968, 80764, 107973, 145638, 195237, 262446, 352904, 474964, 637081, 856232, 1149966, 1543986, 2076534, 2789516

Offset: 0

Author

Antti Karttunen, Oct 12 2017

Keywords

• nonn

Examples

			a(2) = 1 because in the binary tree illustrated in A293230, there is only one node at the level (namely, the node 6) that spawns just one offspring.
		

Crossrefs

Cf. A293230, A293441, A293518, A293519, A293520, A293522.

Programs

PARI

\\ See program at A293520.

Formula

a(n) = Sum_{k=(2^n)..(2^(1+n)-1)} abs(A293233(k)) * [1 == A008966(2*k)+A008966(1+2*k)].

a(n) = A293518(n) + A293519(n). [even survivors + odd survivors.]