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A028987
Repdigit - 1 is prime.
16
3, 4, 6, 8, 44, 444, 888, 2222, 8888, 444444, 888888, 444444444, 888888888, 444444444444, 888888888888, 222222222222222222, 444444444444444444444444444444, 44444444444444444444444444444444
OFFSET
1,1
COMMENTS
Next term is 88...8 (72 digits).
Corresponding values of primes are in A096843. - Jaroslav Krizek, Mar 19 2013
MATHEMATICA
a[n_]:=NestList[FromDigits[Append[{#}, n]]&, n, 35]; Union[Join[{3}, Flatten[Table[Select[a[n], PrimeQ[#-1]&], {n, 2, 8, 2}]]]] (* Jayanta Basu, May 29 2013 *)
PROG
(PARI) u=30; for(n=1, u, r=(10^n-1)/9; for(a=1, 9, m=r*a; if(ispseudoprime(m-1), print1(m, ", ")))) \\ Felix Fröhlich, Jul 07 2014
CROSSREFS
Cf. A010785.
Sequence in context: A084438 A186700 A350217 * A284615 A186709 A143037
KEYWORD
nonn,base
EXTENSIONS
Offset corrected and initial term added by Arkadiusz Wesolowski, Aug 14 2011
STATUS
approved