A068651
Primes in which a string of 2's is sandwiched between two 9's.
Original entry on oeis.org
929, 9222229, 9222222222229
Offset: 1
A068649
Primes in which a string of 9's is sandwiched between two 1's.
Original entry on oeis.org
11, 191, 19991, 199999991, 19999999999999999999999999999999999999991, 199999999999999999999999999999999999999999999999999999999999999999999999999999999999991
Offset: 1
11 is also a member in which a string of 0 9's is there between two one's.
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a := 1:b := 9:i := 1:for n from 0 to 500 do c := a+10*(10^n-1)/9*b+10^(n+1)*a; if(isprime(c)) then d[i] := c; i := i+1; end if; end do:q := seq(d[j],j=1..i-1);
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Select[Table[FromDigits[Join[{1}, Table[9, {i}], {1}]], {i, 0, 200}], PrimeQ]
A082700
Numbers k such that (15*10^(k-1) - 51)/9 is a plateau prime.
Original entry on oeis.org
5, 13, 17, 19, 37, 53, 73, 101, 6233, 24029, 40223, 66395
Offset: 1
k=13 -> (15*10^(13-1) - 51)/9 = 1666666666661.
- C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 28, No. 1, 1996-97, pp. 1-9.
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
A056247
Indices of primes in sequence defined by A(0) = 11, A(n) = 10*A(n-1) + 51 for n > 0.
Original entry on oeis.org
0, 3, 11, 15, 17, 35, 51, 71, 99, 6231, 24027, 40221, 66393
Offset: 1
16661 is prime, hence 3 is a term.
- Klaus Brockhaus and Walter Oberschelp, Zahlenfolgen mit homogenem Ziffernkern, MNU 59/8 (2006), pp. 462-467.
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Select[Range[0, 2000], PrimeQ[(150 10^# - 51) / 9] &] (* Vincenzo Librandi, Nov 03 2014 *)
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a=11;for(n=0,1500,if(isprime(a),print1(n,","));a=10*a+51)
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for(n=0,1500,if(isprime((150*10^n-51)/9),print1(n,",")))
Additional comments from
Klaus Brockhaus and Walter Oberschelp (oberschelp(AT)informatik.rwth-aachen.de), Dec 28 2004
More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
Added one more term from the PDP table and a link, by
Patrick De Geest, Nov 02 2014
Showing 1-4 of 4 results.
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