A118782 Numbers k such that closest primes surrounding 10^n have the same last digit.

6, 9, 12, 19, 20, 23, 28, 31, 32, 33, 39, 59, 62, 66, 67, 75, 79, 80, 83, 84, 85, 91, 98, 99, 107, 108, 109, 117, 121, 144, 147, 149, 150, 153, 155, 156, 159, 160, 167, 169, 178, 179, 184, 186, 187, 191, 195, 208, 210, 212, 220, 222, 226, 227, 229, 231, 242, 246

Offset

1,1

Comments

Do these numbers continue to infinity?

Links

Table of n, a(n) for n=1..58.

Example

999983 and 1000003 are the closest primes surrounding 10^6. they both have the same last digit so 6 is in the table.

Mathematica

Select[Range[246], Mod[NextPrime[10^#], 10]==Mod[NextPrime[10^#, -1], 10]&] (* James C. McMahon, Sep 13 2024 *)

Prog

(PARI) g(n) = for(j=1, n, x=precprime(10^j); y=nextprime(10^j); if(x%10==y%10, print1(j", ")))

Crossrefs

Sequence in context: A023386 A036999 A290130 * A246356 A335065 A315960

Adjacent sequences: A118779 A118780 A118781 * A118783 A118784 A118785

Keyword

easy,nonn,base,less

Author

Cino Hilliard, May 22 2006

Status

approved