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A177014
a(n) is the smallest number m such that all the n numbers 1!*m+1, 2!*m+1, ..., n!*m+1 are prime.
1
1, 1, 1, 18, 18, 8628, 748668, 2506980, 228698250, 228698250
OFFSET
1,4
EXAMPLE
a(5)=18 because each of the five numbers 1!*18+1, 2!*18+1, 3!*18+1, 4!*18+1 and 5!*18+1 is prime, and 18 is the smallest such number.
The corresponding primes are:
n=1: 2;
n=2: 2, 3;
n=3: 2, 3, 7;
n=4: 19, 37, 109, 433;
n=5: 19, 37, 109, 433, 2161;
n=6: 8629, 17257, 51769, 207073, 1035361, 6212161;
n=7: 748669, 1497337, 4492009, 17968033, 89840161, 539040961, 3773286721;
...
PROG
(PARI) okm(m, n) = {for (k=1, n, if (! isprime(k!*m+1), return (0)); ); return (1); }
a(n) = {m = 1; while(! okm(m, n), m++); m; } \\ Michel Marcus, Jun 08 2014
CROSSREFS
Cf. A177013.
Sequence in context: A050686 A165839 A372457 * A355045 A357800 A004459
KEYWORD
more,nonn
AUTHOR
EXTENSIONS
a(10) corrected by Jon E. Schoenfield, Mar 07 2018
STATUS
approved