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%I #5 Mar 21 2016 07:51:44
%S 9,9,27,25,81,125,225,225,361,441,1089,1089,1225,1225,2025,2025,2601,
%T 3249,3249,3375,3721,5041,6859,7569,7921,12321,13689,13689,15129,
%U 18225,21609,21609,30625,31329,38809,42025,47961,53361,59049,65025,65025
%N Powers of the form 2*prime(n)-prime(n+1).
%F a(n)=2*prime(n)-prime(n+1) and a(n) is a power.
%e a(20)=2*prime(478)-prime(479)=2*3391-3407=3375=15^3.
%p with(numtheory); egcd := proc(n) local L; L:=map(proc(z) z[2] end, ifactors(n)[2]); igcd(op(L)) end: PW:=[]: cnt:=0: for z to 1 do for j from 1 to 50000 do x:=2*ithprime(j)-ithprime(j+1); if egcd(x)>1 then cnt:=cnt+1; PW:=[op(PW),[cnt,j,x]] fi od od; PW; map(proc(z) z[3] end, PW);
%Y Cf. A062234.
%K nonn
%O 1,1
%A _Walter Kehowski_, Oct 02 2005
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