A141864 - OEIS

%I #6 Oct 04 2015 01:44:34

%S 1,5,5,8,6,9,8,8,10,8,9,10,11,10,8,9,11,10,13,8,13,9,9,14,11,7,11,11,

%T 12,14,11,10,12,10,10,11,12,12,10,14,8,14,12,13,10,12,14,8,14,12,13,

%U 11,11,11,14,7,16,12,14,9,9,16,12,11,14,11,10,14,12,14,17,8,12,10,15,12,15,12

%N Frequency of A038511 in the interval [(n-1)*3*5*7,n*3*5*7].

%C A value of A038511(0)=1 is artificially introduced which leads to a(1)=1 by definition.

%e In the 2nd interval from 105 to 210 we find A038511(1)=121, A038511(2)=143, A038511(3)=169,

%e A038511(4)=187 and A038511(5)=209, that is a(2)=5 entries.

%e In the 3rd interval from 210 to 315 we find A038511(6)=221, A038511(7)=247, A038511(8)=253,

%e A038511(9)=289 and A038511(10)=299, that is a(3)=5 entries.

%p isA038511 := proc(n) local pfs; if isprime(n) then false; else pfs := numtheory[factorset](n) ; RETURN( pfs intersect {2,3,5,7} = {}) ; fi; end:

%p A141864 := proc(n) local k,a ; if n = 1 then 1; else a := 0 ; for k from (n-1)*105 to n*105 do if isA038511(k) then a := a+1 ; fi; od: a; fi; end:

%p seq(A141864(n),n=1..90) ; # _R. J. Mathar_, Aug 03 2009

%Y Cf. A002808, A141468, A038511.

%K nonn

%O 1,2

%A _Juri-Stepan Gerasimov_, Sep 15 2008

%E Edited, a(13) corrected by _R. J. Mathar_, Aug 03 2009