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%I #7 Apr 06 2018 15:02:27
%S 7,12,20,30,44,62,85,115,150,194,247,310,386,477,583,710,858,1030,
%T 1232,1464,1734,2043,2400,2809,3270,3798,4396,5073,5838,6702,7675,
%U 8768,9997,11370,12905,14615,16528,18658,21024,23655,26570,29798,33372,37324,41685
%N a(1) = 7; a(n+1) = a(n)-th nonprime, where nonprimes begin at 1.
%t With[{np=Select[Range[100000],!PrimeQ[#]&]},NestList[np[[#]]&,7,50]] (* _Harvey P. Dale_, Apr 06 2018 *)
%K nonn
%O 1,1
%A _David W. Wilson_