%I
%S 1,3,4,1,7,9,2,5,4,13,15,17,19,21,4,3,16,25,27,20,9,18,13,33,35,19,18,
%T 39,41,43,28,17,47,49,51,53,55,57,59,61,39,24,65,67,69,71,35,38,75,77,
%U 79,81,47,36,85,87,89,23,68,71,10,12,95,97,99,101,103,40,65,107,109,100
%N Number of n's in A076411.
%C Equals {1} union A053289.  _Tom Verhoeff_, Jan 06 2008
%C Further comments from _Tom Verhoeff_, Jan 06 2008: (Start)
%C In general, for any nonnegative increasing sequence A (offset 1), i.e., with 0 <= A(i) < A(i+1), define
%C F = 'first differences of A' (offset 1), i.e., F(n) = A(n+1)  A(n)
%C L = 'number of A(i) less than n' (offset 1)
%C M = 'number of values at most n in L' (offset 0; auxiiliary sequence)
%C N = 'number of n's in L' (offset 0). Then M = A, i.e. M(k) = A(k+1), N = [ A(1) ] union F.
%C Proof: Observe that L is nonnegative and ascending: 0 <= L(i) <= L(i+1).
%C M(0) = N(0) = number of 0's in L = number of i >= 0 such that no A(j) < i = min A = A(1)
%C For k > 0, M(k) = number of values at most k in L = A(k+1)
%C N(k) = number of k's in L = number i >= 0 such that exactly k A(j) < i = M(k)  M(k1) = A(k+1)  A(k) = F(k). QED (End)
%C First difference of perfect powers: A001597 prepended by 1.  _Robert G. Wilson v_, May 21 2009
%C Question: Does every number appear at least once? See the comment in A053289.  _Robert G. Wilson v_, May 21 2009
%H Robert G. Wilson v, <a href="/A076412/b076412.txt">Table of n, a(n) for n = 0..10488</a>
%e a(9)=13 because 9 appears 13 times in A076411.
%t t = Join[{0, 1}, Select[ Range@ 3600, GCD @@ Last /@ FactorInteger@# > 1 &]]; Rest@t  Most@t (* _Robert G. Wilson v_, May 21 2009 *)
%Y Cf. A001597, A076411.
%Y Cf. A053289.
%K nonn
%O 0,2
%A _Zak Seidov_, Oct 09 2002
%E a(19)a(71) from _Robert G. Wilson v_, May 21 2009
