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A108818 Primes such that the outer 2 digits are n and n+1 and all inner digits are 1, where 0 < n < 9. 1
617, 2113, 81119, 21111113, 81111119, 8111111119, 21111111111113, 81111111111111111119, 81111111111111111111119, 2111111111111111111111113, 2111111111111111111111111111113, 611111111111111111111111111111117 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
The first digit of each term must be 2, 6, or 8. - Harvey P. Dale, Jun 14 2020
LINKS
FORMULA
a(x) = 10^(x+1)*n+floor(10^x/9)*10+n+1. Output if a(x) is prime.
MATHEMATICA
Select[Flatten[Table[FromDigits[Join[PadRight[{k}, n, 1], {k+1}]], {n, 2, 40}, {k, {2, 6, 8}}]], PrimeQ] (* Harvey P. Dale, Jun 14 2020 *)
PROG
(PARI) n10np1(n) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+floor(10^x/9)*10+k+1; if(isprime(y), print1(y", ")) ) ) }
CROSSREFS
Sequence in context: A275048 A350083 A275739 * A288412 A234559 A251323
KEYWORD
easy,nonn,base
AUTHOR
Cino Hilliard, Jul 11 2005
STATUS
approved

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Last modified May 23 18:34 EDT 2024. Contains 372765 sequences. (Running on oeis4.)