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Numbers n such that A051885(p_n) is prime, where p_n=A000040(n) is the n-th prime.
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%I #27 Dec 15 2017 17:34:52

%S 1,2,3,4,5,7,8,9,10,11,13,14,20,22,25,40,41,55,57,64,77,125,663,1053,

%T 1414,1711,2822,2956,4107,7463

%N Numbers n such that A051885(p_n) is prime, where p_n=A000040(n) is the n-th prime.

%C Numbers n such that A051885(A000040(n)) = A054750(n).

%C No other terms below 10^4.

%e The 125th prime is 691. The least integer with sum of digits 691 is A051885(691) = 8*10^76-1 which is prime. This is the 22nd prime with this property, so a(22)=125.

%o (PARI) for(X=1,300, a=prime(X)%9; b=prime(X)\9; m=(a+1)*10^b-1; if(isprime(m), print([X,prime(X),m]) ) )

%Y Cf. A054750, A051885.

%K more,nonn,base

%O 1,2

%A Kok Seng Chua (chuaks(AT)ihpc.nus.edu.sg), May 31 2000

%E More terms from _Jason Earls_, Jun 22 2001

%E a(27)-a(30) from _Max Alekseyev_, Dec 09 2011