A108830 Primes such that the outer 2 digits are n and n-1 and all inner digits are 2, where 0 < n < 9.

827, 2221, 42223, 4222222223, 42222222223, 222222222222222221, 822222222222222222227, 42222222222222222222222222222223, 8222222222222222222222222222222227, 822222222222222222222222222222222222222222222222222222222222227

Offset

1,1

Links

Table of n, a(n) for n=1..10.

Mathematica

Sort[Select[Flatten[Table[FromDigits[Join[{n}, PadRight[{}, i, 2], {n-1}]], {n, 2, 8, 2}, {i, 70}]], PrimeQ]] (* Harvey P. Dale, Dec 05 2015 *)

Prog

(PARI) n10np1(n, d) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+floor(10^x*d/9)*10+k-1; if(isprime(y), print1(y", ")) ) ) }

Crossrefs

Sequence in context: A143799 A046496 A102350 * A341272 A340115 A134726

Adjacent sequences: A108827 A108828 A108829 * A108831 A108832 A108833

Keyword

easy,nonn,base

Author

Cino Hilliard, Jul 11 2005

Extensions

One more term (a(10)) from Harvey P. Dale, Dec 05 2015

Status

approved