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%I #5 Mar 30 2012 17:34:14
%S 520,2397,3500,3518,3826,4439,4662,6620,7518,8926,9206,10220,10780,
%T 10938,12498,12640,12740,14049,14358,18623,20118,20262,22569,24419,
%U 25300,25706,26920,27498,28482,29500,30398,30438,31600,31820,31986
%N Average of 4 primes where the integer Schwarzian derivative is zero.
%F a(n) = if Sf(Prime[n])=0 then (Prime[n-3]+Prime[n-2]+Prime[n-1]+Prime[n])/2
%t f1[n_]=Prime[n]-Prime[n-1] f2[n_]=Prime[n]-2*Prime[n-1]+Prime[n-2] f3[n_]=Prime[n]-3*Prime[n-1]+3*Prime[n-2]-Prime[n-3] sf[n_]=f3[n]/f1[n]-1.5*(f2[n]/f1[n])^2 a=Delete[Union[Table[If[sf[n]==0, (Prime[n-3]+Prime[n-2]+Prime[n-1]+Prime[n])/2, 0], {n, 4, 2004}]], 1]
%K nonn
%O 4,1
%A _Roger L. Bagula_, Jun 15 2004
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