

A121837


Least positive j such that Product_{k=1..n} D(k) + j is prime, where D() are the doublets, A020338.


1



2, 9, 7, 7, 17, 7, 29, 17, 19, 23, 23, 13, 29, 79, 19, 89, 97, 53, 43, 347, 127, 127, 149, 29, 167, 331, 379, 61, 59, 167, 199, 557, 107, 113, 43, 191, 439, 41, 263, 227, 109, 71, 227, 137, 149, 409, 271, 53, 157, 79, 503, 103, 461, 137, 587, 233, 491, 73, 367, 233, 449
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

Is every term for n > 2 always prime?
a(n) = 1 for n = 245 and 702 (using ispseudoprime() in PARI).  Michel Marcus, Jan 08 2021


LINKS



FORMULA



PROG

(PARI) D(n) = eval(Str(n, n)); \\ A020338
f(n) = prod(k=1, n, D(k)); \\ A121826
a(n) = my(q=f(n)); nextprime(q+1)  q; \\ Michel Marcus, Jan 07 2021


CROSSREFS



KEYWORD

nonn,base


AUTHOR



STATUS

approved



