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A175027 Replace prime with its index! 5

%I #4 Jul 16 2015 22:01:45

%S 0,1,1,2,4,3,6,4,8,9,10,5,12,6,14,15,16,7,18,8,20,21,22,9,24,25,26,27,

%T 28,10,30,11,32,33,34,35,36,12,38,39,40,13,42,14,44,45,46,15,48,49,50,

%U 51,52,16,54,55,56,57,58,17,60,18,62,63,64,65,66,19,68,69,70,20,72,21

%N Replace prime with its index!

%F a(n)=n if n is nonprime otherwise a(n)=primepi(n).

%t Table[If[PrimeQ[n],PrimePi[n],n],{n,0,200}]

%Y Cf. A068519.

%K nonn

%O 0,4

%A _Zak Seidov_, Nov 04 2009

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Last modified July 25 07:50 EDT 2024. Contains 374586 sequences. (Running on oeis4.)