OFFSET
0,4
COMMENTS
This sequence may be related to n-ary rooted trees of a fixed height. For instance, the first few terms of A036616 are:
1, 1, 1, 2, 4, 9, 19, 41, 86, 182, 376, 776, 1579, ...
and in A036622:
1, 1, 1, 2, 4, 9, 19, 42, 88, 188, 393, 821, 1692, ...
whereas in the present sequence we have:
0, 0, 0, 2, 3, 9, 19, 41, 85, 181, 375, 769, 1584, ...
FORMULA
Members of A071904 that lie between 2^n and 2^(n + 1).
EXAMPLE
a(3) = 2 because in the interval 2^3..2^4 = [8..16] there are two odd composites: 9 = 3^2, 15 = 3 * 5.
MATHEMATICA
f[n_] := (2^(n - 1) - PrimePi[2^(n + 1)] + PrimePi[2^n]); Table[ f[n], {n, 32}] (* Robert G. Wilson v, Jun 15 2004 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Andrew S. Plewe, Jun 11 2004
EXTENSIONS
More terms from Robert G. Wilson v, Jun 15 2004
STATUS
approved