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 A103800 Indices n such that A019565(n)-2 is prime. 1

%I

%S 4,6,8,10,14,18,20,22,26,28,30,32,34,38,40,42,54,58,60,62,68,76,78,86,

%T 88,98,100,102,106,110,126,128,134,136,138,142,158,162,174,188,190,

%U 194,196,202,210,218,222,230,234,238,240,254,258,260,272,274,278,292,294

%N Indices n such that A019565(n)-2 is prime.

%e A019565(0)=1, 1-2=-1 is not prime;

%e A019565(1)=2, 2-2=0 is not prime;

%e ...

%e A019565(4)=5, 5-2=3 is prime, so a(1)=4;

%t A019565 = Function[tn, k1 = tn; o = 1; tt = 1; While[k1 > 0, k2 = Mod[k1, 2]; If[k2 == 1, tt = tt*Prime[o]]; k1 = (k1 - k2)/2; o = o + 1]; tt]; Do[cp = A019565[n] - 2; If[PrimeQ[cp], Print[n]], {n, 0, 1000}]

%Y Cf. A019565, A103799.

%K easy,nonn

%O 1,1

%A _Lei Zhou_, Feb 22 2005

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Last modified December 6 09:25 EST 2019. Contains 329791 sequences. (Running on oeis4.)