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%I #8 Mar 30 2012 18:50:44
%S 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,1,1,1,1,2,2,2,2,2,2,
%T 2,2,2,2,2,2,3,3,4,4,4,4,4,4,4,4,4,4,5,5,5,5,5,5,7,7,7,7,7,7,7,7,7,7,
%U 7,7,7,7,7,7,7,7,7,7,8,8,8,8,9,9,9,9,9,9,9,9,9,9,9,9,9,9,11,11,11,11
%N Number of quadruples (p, p+d, p+2*d, p+3*d) of primes with d>0 and p+3*d<=n.
%H <a href="/index/Pri#primes_AP">Index entries for sequences related to primes in arithmetic progressions</a>
%e a(50)=4: 5=prime(3) -> 5+6=11=prime(5) -> 11+6=17=prime(7) ->
%e 17+6=23=prime(9), 5=prime(3) -> 5+12=17=prime(7) -> 17+12=29=prime(10) ->
%e 29+12=41=prime(13), 7=prime(4) -> 7+12=19=prime(8) -> 19+12=31=prime(11) ->
%e 31+12=43=prime(14) and 11=prime(5) -> 11+6=17=prime(7) -> 17+6=23=prime(9)
%e -> 23+6=29=prime(10),
%Y Cf. A093354, A094383.
%K nonn
%O 1,29
%A _Reinhard Zumkeller_, Apr 28 2004
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