A062225
Numbers k such that the smoothly undulating palindromic number (78*10^k - 87)/99 is a prime.
Original entry on oeis.org
3, 5, 21, 27, 95, 2075, 2165, 3047, 3503, 16791, 34883
Offset: 1
Patrick De Geest and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001
k=21 -> (78*10^21 - 87)/99 = 787878787878787878787.
A062226
Numbers k such that the smoothly undulating palindromic number (79*10^k - 97)/99 is a prime.
Original entry on oeis.org
3, 357, 537, 1677, 3057, 51663, 66447
Offset: 1
Patrick De Geest and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001
k=357 -> (79*10^357 - 97)/99 = 7979797...7979797.
A062227
Numbers k such that the smoothly undulating palindromic number (91*10^k - 19)/99 is a prime.
Original entry on oeis.org
3, 9, 11, 17, 23, 25229
Offset: 1
Patrick De Geest and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001
k=23 -> (91*10^23 - 19)/99 = 91919191919191919191919.
A062228
Numbers k such that the smoothly undulating palindromic number (92*10^k - 29)/99 is a prime.
Original entry on oeis.org
3, 9, 195, 515, 857, 11393
Offset: 1
Patrick De Geest and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001
k=9 -> (92*10^9 - 29)/99 = 929292929.
A062229
Numbers k such that the smoothly undulating palindromic number (94*10^k - 49)/99 is a prime.
Original entry on oeis.org
5, 17, 65, 143, 551, 92981
Offset: 1
Patrick De Geest and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001
k=17 -> (94*10^17 - 49)/99 = 94949494949494949.
A062230
Numbers k such that the smoothly undulating palindromic number (95*10^k - 59)/99 is a prime.
Original entry on oeis.org
5, 17, 209, 1295
Offset: 1
Patrick De Geest and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001
k=17 -> (95*10^17 - 59)/99 = 95959595959595959.
A242846
Palindromic primes of the form ababa...aba containing only the digits 1 and 3.
Original entry on oeis.org
131, 313, 1313131313131313131313131, 313131313131313131313131313131313131313131313131313
Offset: 1
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Module[{nn=60,a,b},a=Table[FromDigits[Join[PadRight[{},2n,{1,3}],{1}]],{n,nn}];b=Table[FromDigits[Join[PadRight[{},2n,{3,1}],{3}]],{n,nn}];Select[Sort[Join[a,b]],PrimeQ]] (* Harvey P. Dale, Sep 07 2020 *)
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