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 A028987 Repdigit - 1 is prime (next term is 88...8 (72 digits)). 15
 3, 4, 6, 8, 44, 444, 888, 2222, 8888, 444444, 888888, 444444444, 888888888, 444444444444, 888888888888, 222222222222222222, 444444444444444444444444444444, 44444444444444444444444444444444 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Corresponding values of primes are in A096843. - Jaroslav Krizek, Mar 19 2013. LINKS P. De Geest, Repdigits : WONplate 83 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 FrÃ¶hlich, Jul 07 2014 CROSSREFS Cf. A010785. Sequence in context: A063506 A084438 A186700 * A284615 A186709 A143037 Adjacent sequences:  A028984 A028985 A028986 * A028988 A028989 A028990 KEYWORD nonn,base AUTHOR EXTENSIONS Offset corrected and initial term added by Arkadiusz Wesolowski, Aug 14 2011 STATUS approved

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Last modified August 14 09:14 EDT 2020. Contains 336480 sequences. (Running on oeis4.)