A121815 Least positive k such that (n*10^n+n+1)*10^n+k is prime.

7, 23, 13, 29, 3, 7, 29, 57, 3, 43, 21, 69, 31, 9, 19, 31, 179, 21, 167, 71, 19, 13, 3, 207, 29, 89, 123, 343, 171, 73, 127, 171, 9, 329, 101, 463, 373, 9, 87, 77, 33, 661, 493, 159, 159, 89, 417, 21, 269, 381, 181, 421, 219, 183, 173, 357, 21, 13, 293, 109, 1187, 77

Offset

1,1

Comments

Note that a(87) = 87; any more where k = n?

Links

Michael S. Branicky, Table of n, a(n) for n = 1..1000

Example

a(5)=3 because 50000600003 is prime.

Mathematica

s={}; Do[ k=0; Until[PrimeQ[(n*10^n+n+1)*10^n+k], k++]; AppendTo[s, k], {n, 87}]; s (* James C. McMahon, Oct 22 2024 *)
Table[With[{c=(n*10^n+n+1)10^n}, NextPrime[c]-c], {n, 70}] (* Harvey P. Dale, Dec 12 2024 *)

Crossrefs

Sequence in context: A367003 A167224 A175483 * A025172 A115023 A009228

Adjacent sequences: A121812 A121813 A121814 * A121816 A121817 A121818

Keyword

nonn

Author

Jason Earls, Aug 26 2006

Status

approved