A090263 -id:A090263 - cp's OEIS frontend

A090262 Numbers n such that the strings n1n and 1n1 are both prime.

3, 9, 17, 29, 47, 51, 81, 87, 113, 117, 131, 141, 201, 239, 291, 333, 359, 371, 393, 443, 459, 489, 509, 539, 573, 623, 663, 681, 749, 819, 821, 873, 903, 947, 1071, 1077, 1161, 1269, 1533, 1563, 1589, 1613, 1637, 1673, 1767, 1773, 1821, 1841, 1883, 1959, 1977

Offset: 1

Amarnath Murthy, Nov 28 2003

			9 is a member as 919 and 191 are both prime.

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

Cf. A090263, A090264, A090265.

More terms from mohammed bouayoun (bouyao(AT)wanadoo.fr), Feb 02 2004

A090264 Numbers n such that the strings n7n and 7n7 are both prime.

Original entry on oeis.org

131, 153, 191, 233, 261, 327, 341, 359, 389, 407, 429, 459, 489, 527, 533, 579, 593, 599, 671, 683, 701, 723, 731, 797, 813, 869, 873, 939, 981, 1083, 1097, 1109, 1143, 1187, 1241, 1283, 1317, 1391, 1437, 1451, 1539, 1553, 1871, 1889, 1893, 2049, 2111

Offset: 1

Amarnath Murthy, Nov 28 2003

			131 is a member as 1317131 and 71317 are both prime.

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000

Cf. A090262, A090263, A090265.

More terms from mohammed bouayoun (bouyao(AT)wanadoo.fr), Feb 02 2004

A090265 Numbers n such that the strings n9n and 9n9 are both prime.

Original entry on oeis.org

1, 19, 41, 43, 47, 61, 67, 71, 73, 83, 107, 149, 211, 217, 221, 269, 277, 319, 437, 443, 523, 547, 553, 607, 619, 647, 679, 697, 817, 863, 877, 899, 1171, 1283, 1297, 1379, 1481, 1547, 1621, 1853, 1867, 1967, 1993, 1997, 2021, 2053, 2107, 2357, 2359, 2393

Offset: 1

Amarnath Murthy, Nov 28 2003

			41 is a member as 41941 and 9419 are both prime.

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Cf. A090262, A090263, A090264.

n9Q[n_]:=Module[{idn=IntegerDigits[n]},AllTrue[{FromDigits[Join[idn,{9}, idn]],FromDigits[ Join[{9},idn,{9}]]},PrimeQ]]; Select[Range[2500],n9Q] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Feb 01 2016 *)

More terms from mohammed bouayoun (bouyao(AT)wanadoo.fr), Feb 02 2004

A101472 Numbers k such that the number k33 is prime.

Original entry on oeis.org

2, 4, 7, 10, 14, 17, 19, 23, 26, 28, 34, 35, 37, 38, 41, 47, 49, 52, 53, 61, 67, 68, 73, 74, 79, 82, 89, 91, 94, 95, 97, 98, 101, 103, 104, 107, 116, 118, 119, 124, 130, 136, 139, 140, 145, 146, 152, 157, 160, 163, 164, 166, 170, 173, 181, 182, 184, 193, 194, 202

Offset: 1

Parthasarathy Nambi, Jan 30 2005

			If k=2,  then k33 =  233 (prime);
If k=34, then k33 = 3433 (prime);
If k=74, then k33 = 7433 (prime).

Daniel Starodubtsev, Table of n, a(n) for n = 1..10000
Chris Caldwell The first 1,000 primes.

Cf. A090263, A109369.

[n: n in [0..250] | IsPrime(Seqint(Intseq(33) cat Intseq(n)))]; // Vincenzo Librandi, Jul 31 2015

fQ[n_] := PrimeQ[FromDigits[ Join[ IntegerDigits[n], {3, 3}]]]; Select[ Range[203], fQ[ # ] &] (* Robert G. Wilson v, Feb 04 2005 *)
Select[Range[250], PrimeQ[FromDigits[Flatten[{IntegerDigits[#], IntegerDigits[33]}]]] &] (* Vincenzo Librandi, Jul 31 2015 *)
Select[Range[210],PrimeQ[100#+33]&] (* Harvey P. Dale, Jul 04 2017 *)

is(n)=isprime(100*n+33) \\ Charles R Greathouse IV, May 22 2017

More terms from Robert G. Wilson v, Feb 04 2005

cp's OEIS Frontend

A090262 Numbers n such that the strings n1n and 1n1 are both prime.

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A090264 Numbers n such that the strings n7n and 7n7 are both prime.

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A090265 Numbers n such that the strings n9n and 9n9 are both prime.

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Mathematica

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A101472 Numbers k such that the number k33 is prime.

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Magma

Mathematica

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