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A261033 Values of n such that A002110(n) - A007504(n) - 1 is a prime number. 0

%I #33 Nov 25 2015 02:23:39

%S 3,5,7,9,13

%N Values of n such that A002110(n) - A007504(n) - 1 is a prime number.

%C Values of n such that difference between product of first n+1 terms of A008578 and sum of first n+1 terms of A008578 is a prime number.

%C Initial primes of the form A002110(n) - A007504(n) - 1 are 19, 2281, 510451.

%e a(1) = 3 because (2*3*5) - (2+3+5) - 1 = 19 is prime.

%e a(2) = 5 because (2*3*5*7*11) - (2+3+5+7+11) - 1 = 2281 is prime.

%e a(3) = 7 because (2*3*5*7*11*13*17) - (2+3+5+7+11+13+17) - 1 = 510451 is prime.

%o (PARI) for(n=1, 1e5, if(ispseudoprime(prod(k=1, n, prime(k)) - sum(k=1, n, prime(k)) - 1), print1(n, ", ")));

%Y Cf. A002110, A007504, A008578, A014284.

%K nonn,more

%O 1,1

%A _Altug Alkan_, Nov 18 2015

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