This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A078435 Number of composites <= n^2. 4

%I

%S 1,2,5,10,16,25,34,46,59,75,91,110,130,152,177,202,228,258,289,322,

%T 356,392,430,471,511,554,600,647,695,746,799,852,908,965,1025,1086,

%U 1150,1216,1281,1349,1418,1490,1566,1641,1719,1797,1880,1962,2044,2133,2223

%N Number of composites <= n^2.

%F a(n) = n^2 - A038107(n). - _R. J. Mathar_, Jun 22 2009

%e a(3)=5 because the only composites <= 9 are 1, 4, 6, 8 and 9.

%p NumComposites := proc(N::posint) local count, i:count := 0:for i from 1 to N do if not isprime(i) then count := count + 1 fi:od: count;end:seq(NumComposites(k^2), k=1..51); # _Zerinvary Lajos_, May 26 2008

%p A038107 := proc(n) numtheory[pi]( n^2) ; end: A078435 := proc(n) n^2-A038107(n) ; end: seq(A078435(n),n=1..100) ; # _R. J. Mathar_, Jun 22 2009

%K nonn

%O 1,2

%A John E. Lenz (jel5010(AT)yahoo.com), Dec 30 2002

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified March 26 23:09 EDT 2019. Contains 321566 sequences. (Running on oeis4.)