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 A108837 Primes of the form 5*10^n-7. 2
 43, 4993, 49993, 499999993, 499999999999993, 49999999999999993, 4999999999999999999999993, 49999999999999999999999999999999999999999999999999999999999993 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes such that the leftmost digit is 4, the rightmost digit is 3, and all inner digits are 9. LINKS Makoto Kamada, Prime numbers of the form 499...993. FORMULA a(n) = 5*10^A103002(n) - 7. MATHEMATICA Select[Table[FromDigits[Join[PadRight[{4}, n+1, 9], {3}]], {n, 0, 150}], PrimeQ] (* Harvey P. Dale, Feb 01 2012 *) PROG (PARI) n10np9(n, d) = { local(x, y, k); for(x=1, n, for(k=1, 8, y=10^(x+1)*k+(10^x-1)*10+k-1; if(isprime(y), print1(y", ")) ) ) } (MAGMA)[a: n in [1..250]|IsPrime(a) where a is (5*10^n-7)] // Vincenzo Librandi, Dec 11 2010 (PARI) for(n=4, 99, if(ispseudoprime(t=10^n/2-7), print1(t", "))) \\ Charles R Greathouse IV, Feb 01 2012 CROSSREFS Cf. A103002, A101739. Sequence in context: A110704 A060485 A081795 * A091748 A208625 A147522 Adjacent sequences:  A108834 A108835 A108836 * A108838 A108839 A108840 KEYWORD easy,nonn,base AUTHOR Cino Hilliard, Jul 11 2005 EXTENSIONS Edited by Ray Chandler, Feb 03 2012 Comments amended by Harvey P. Dale, Feb 03 2012 STATUS approved

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Last modified June 6 04:15 EDT 2020. Contains 334859 sequences. (Running on oeis4.)