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A261033

Values of k such that A002110(k) - A007504(k) - 1 is a prime number.

3, 5, 7, 9, 13

OFFSET

1,1

COMMENTS

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

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

a(6) > 30000. - Michael S. Branicky, Mar 16 2026

LINKS

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

URL: https://oeis.org/A261033