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%I #15 Jul 04 2016 11:05:35
%S 3,4,1,7,9,2,5,17,15,17,40,4,3,41,74,13,33,54,18,151,17,96,104,112,
%T 120,63,307,38,312,168,199,139,10,12,192,408,316,356,240,375,393,424,
%U 128,288,912,320,298,30,1032,271,1217,792,408,840,432,286,602,1872,984,504
%N First differences of A025475, powers of a prime but not prime.
%C In the graph of this sequence, the lowest curve corresponds to differences of squares of twin primes; the next-lowest curve is for squares of adjacent primes differing by 4, etc. - _T. D. Noe_, Aug 03 2007
%H T. D. Noe, <a href="/A053707/b053707.txt">Table of n, a(n) for n=1..10000</a>
%F a(n) = A025475(n+1) - A025475(n).
%e 2^0 = 1 is the first number that meets the definition of A025475, the next one is 2^2 = 4, hence a(1) = 4 - 1 = 3.
%e a(3) = A025475(4) - A025475(3) = 9 - 8 = 1; a(11) = A025475(12) - A025475(11) = 121 - 81 = 40.
%t Differences@ Join[{1}, Select[Range@ 16200, And[! PrimeQ@ #, PrimePowerQ@ #] &]] (* _Michael De Vlieger_, Jul 04 2016 *)
%o (PARI) {k=1; for(n=2,16300,if(matsize(factor(n))[1]==1&&factor(n)[1,2]>1,d=n-k; print1(d,","); k=n))} \\ _Klaus Brockhaus_, Sep 25 2003
%Y Cf. A025475.
%K nonn
%O 1,1
%A _Labos Elemer_, Feb 14 2000
%E Edited by _Klaus Brockhaus_, Sep 25 2003
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