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A261033
Values of n such that A002110(n) - A007504(n) - 1 is a prime number.
0
3, 5, 7, 9, 13
OFFSET
1,1
COMMENTS
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.
Initial primes of the form A002110(n) - A007504(n) - 1 are 19, 2281, 510451.
EXAMPLE
a(1) = 3 because (2*3*5) - (2+3+5) - 1 = 19 is prime.
a(2) = 5 because (2*3*5*7*11) - (2+3+5+7+11) - 1 = 2281 is prime.
a(3) = 7 because (2*3*5*7*11*13*17) - (2+3+5+7+11+13+17) - 1 = 510451 is prime.
PROG
(PARI) for(n=1, 1e5, if(ispseudoprime(prod(k=1, n, prime(k)) - sum(k=1, n, prime(k)) - 1), print1(n, ", ")));
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Nov 18 2015
STATUS
approved