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 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(159) = 1. - Michel Marcus, Jan 07 2021 a(n) = 1 for n = 245 and 702 (using ispseudoprime() in PARI). - Michel Marcus, Jan 08 2021 LINKS Michel Marcus, Table of n, a(n) for n = 1..200 FORMULA a(n) = A013632(A121826(n)). - Michel Marcus, Jan 07 2021 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 Cf. A013632, A020338, A121826, A151800. Sequence in context: A021340 A241753 A157350 * A160439 A245287 A254595 Adjacent sequences: A121834 A121835 A121836 * A121838 A121839 A121840 KEYWORD nonn,base AUTHOR Jason Earls, Aug 28 2006 STATUS approved

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Last modified December 6 01:37 EST 2023. Contains 367594 sequences. (Running on oeis4.)