cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Previous Showing 21-29 of 29 results.

A023281 Primes that remain prime through 3 iterations of function f(x) = 4x + 3.

Original entry on oeis.org

2, 109, 179, 571, 677, 977, 1279, 1447, 1747, 1901, 2207, 2671, 3119, 3917, 5011, 5399, 5441, 5569, 5791, 6211, 6607, 7079, 7417, 8369, 8831, 9221, 9697, 9769, 11821, 11897, 12347, 13537, 13669, 13691, 13729, 13781, 13907, 14747, 14851, 15581, 17231, 17497
Offset: 1

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Author

Keywords

Comments

Primes p such that 4*p+3, 16*p+15 and 64*p+63 are also primes. - Vincenzo Librandi, Aug 04 2010

Crossrefs

Subsequence of A023213, A023250, and of A095278.

Programs

  • Magma
    [n: n in [1..150000] | IsPrime(n) and IsPrime(4*n+3) and IsPrime(16*n+15) and IsPrime(64*n+63)] // Vincenzo Librandi, Aug 04 2010
    
  • Maple
    f:=proc(x) options operator, arrow: 4*x+3 end proc: a:=proc(n) if isprime(n)= true and isprime(f(n))=true and isprime(f(f(n)))=true and isprime(f(f(f(n)))) =true then n else end if end proc: seq(a(n),n=1..20000); # Emeric Deutsch, Jan 01 2008
  • Mathematica
    Select[Prime@ Range@ 2100, Times @@ Boole@ PrimeQ@ Rest@ NestList[4 # + 3 &, #, 3] > 0 &] (* Michael De Vlieger, Sep 19 2016 *)
  • PARI
    is(n)=isprime(n) && isprime(4*n+3) && isprime(16*n+15) && isprime(64*n+63) \\ Charles R Greathouse IV, Sep 20 2016

A105135 Numbers n such that 32n+17 is prime.

Original entry on oeis.org

0, 3, 7, 10, 12, 13, 18, 27, 30, 31, 37, 40, 42, 46, 48, 55, 58, 66, 67, 75, 81, 87, 88, 90, 96, 97, 100, 103, 115, 117, 118, 121, 126, 130, 132, 133, 135, 142, 145, 147, 150, 156, 163, 165, 168, 172, 195, 198, 201, 202, 205, 208, 210, 213, 217, 220, 222, 235, 243, 250, 252
Offset: 1

Views

Author

N. J. A. Sloane, based on correspondence from Marco Matosic, Apr 11 2005

Keywords

Crossrefs

Programs

A105136 Numbers n such that 64n+33 is prime.

Original entry on oeis.org

1, 5, 10, 14, 19, 26, 29, 31, 32, 35, 40, 41, 47, 49, 52, 56, 62, 64, 70, 80, 82, 91, 95, 104, 115, 116, 119, 122, 127, 130, 134, 136, 139, 146, 151, 160, 161, 164, 166, 179, 181, 182, 196, 197, 206, 211, 214, 217, 221, 224, 227, 230, 235, 236, 239, 244, 250, 251, 256, 257
Offset: 1

Views

Author

N. J. A. Sloane, based on correspondence from Marco Matosic, Apr 11 2005

Keywords

Crossrefs

Programs

A105137 Numbers n such that 128n+65 is prime.

Original entry on oeis.org

1, 3, 4, 9, 12, 16, 21, 24, 33, 36, 37, 42, 43, 46, 49, 54, 58, 61, 66, 67, 72, 79, 81, 88, 93, 94, 102, 103, 106, 112, 114, 123, 124, 126, 138, 148, 154, 157, 163, 166, 168, 177, 186, 187, 196, 198, 199, 201, 204, 207, 211, 213, 214, 219, 231, 232, 238, 252, 256, 262, 264
Offset: 1

Views

Author

N. J. A. Sloane, based on correspondence from Marco Matosic, Apr 11 2005

Keywords

Crossrefs

Programs

A124855 Numbers k such that 3k + 4 and 4k + 3 are primes.

Original entry on oeis.org

1, 5, 11, 19, 25, 31, 41, 49, 59, 65, 89, 91, 109, 115, 121, 125, 151, 161, 179, 181, 205, 209, 229, 241, 245, 275, 305, 329, 331, 349, 355, 361, 371, 389, 415, 439, 509, 515, 521, 535, 551, 595, 599, 625, 661, 665, 671, 719, 725, 749, 755, 769, 779, 791, 839
Offset: 1

Views

Author

Zak Seidov, Nov 10 2006

Keywords

Crossrefs

Intersection of A034936 and A095278. Prime terms are in A106068.

Programs

  • Magma
    [n: n in [0..1000] | IsPrime(3*n+4) and IsPrime(4*n+3)] // Vincenzo Librandi, Mar 26 2010
  • Mathematica
    Select[Range[850], PrimeQ[3# + 4] && PrimeQ[4# + 3] &] (* Ray Chandler, May 11 2007 *)

A244087 Numbers n such that 4*n+3 and 8*n+7 are prime.

Original entry on oeis.org

0, 2, 5, 20, 32, 44, 47, 59, 62, 89, 104, 107, 110, 122, 164, 170, 179, 185, 227, 254, 257, 275, 305, 359, 362, 374, 377, 389, 395, 452, 482, 500, 509, 515, 584, 587, 599, 614, 635, 674, 704, 725, 734, 740, 755, 824, 839, 872, 884, 905, 944, 950, 962, 965, 977
Offset: 1

Views

Author

Vincenzo Librandi, Jun 25 2014

Keywords

Comments

-2 is a primitive root mod (8*n+7).

Crossrefs

Intersection of A095278 and A139487.

Programs

  • Magma
    [n: n in [0..1000] | IsPrime(4*n+3) and IsPrime(8*n+7)];
  • Mathematica
    Select[Range[0, 1500], PrimeQ[4 # + 3]&&PrimeQ[8 # + 7] &]

A254288 Numbers k such that 4*k + {1, 3, 7, 9, 13, 19} are all prime.

Original entry on oeis.org

1, 370, 41425, 81535, 255625, 267175, 311590, 365350, 1054570, 1381750, 2533600, 2975125, 3266080, 3930205, 4684210, 4782385, 4802860, 5940850, 6414610, 7986565, 8429245, 8570470, 8636305, 8810080, 9270715, 9857980, 10459525, 13708225, 13917490, 15127720, 15252460
Offset: 1

Views

Author

K. D. Bajpai, Jan 27 2015

Keywords

Comments

All terms in this sequence are congruent to 1 mod 3.
Subsequence of A123986.

Examples

			a(2) = 370;
4*370 +  1 = 1481;
4*370 +  3 = 1483;
4*370 +  7 = 1487;
4*370 +  9 = 1489;
4*370 + 13 = 1493;
4*370 + 19 = 1499;
All six are prime.
		

Crossrefs

Programs

  • Magma
    [n: n in [0..10^8] | forall{4*n+i: i in [1, 3, 7, 9, 13, 19] |  IsPrime(4*n+i)}]; // Vincenzo Librandi, Mar 12 2015
  • Mathematica
    Select[Range[5*10^7], PrimeQ[4*# + 1] && PrimeQ[4*# + 3] && PrimeQ[4*# + 7] && PrimeQ[4*# + 9] && PrimeQ[4*# + 13] && PrimeQ[4*# + 19] &]
    Select[Range[5*10^6], And @@ PrimeQ /@ ({1, 3, 7, 9, 13, 19} + 4 #) &]
  • PARI
    for(n=1,10^7, if( isprime(4*n + 1) && isprime(4*n + 3) &&isprime(4*n + 7) &&isprime(4*n + 9) &&isprime(4*n + 13) &&isprime(4*n + 19) , print1(n,", ")))
    

A254376 Numbers n such that 4n+1, 4n+3, 4n+7, 4n+9 and 4n+13 are prime.

Original entry on oeis.org

1, 25, 370, 4015, 4855, 10945, 36040, 41425, 41710, 50455, 56335, 61900, 81535, 86995, 116290, 129700, 134110, 158365, 207430, 239635, 255625, 265990, 267175, 272815, 293395, 311590, 335080, 337810, 339700, 342115, 365350, 393385, 403960, 481345, 488590, 550990
Offset: 1

Views

Author

K. D. Bajpai, Jan 29 2015

Keywords

Comments

All terms in this sequence are 1 mod 3.
Each term yields a set of five consecutive primes.
Alternatively: Numbers n such that 4n+k forms a set of five consecutive primes for k = {1,3,7,9,13}.
Subsequence of A123986.

Examples

			25 is in the list because 4*25 + 1 = 101, 4*25 + 3 = 103, 4*25 + 7 = 107, 4*25 + 9 = 109 and 4*25 + 13 = 113 are all prime.
		

Crossrefs

Programs

  • Magma
    [n: n in [0..10^6] | forall{4*n+r: r in [1,3,7,9,13] | IsPrime(4*n+r)}]; // Vincenzo Librandi, Feb 16 2015
  • Mathematica
    Select[Range[1, 500000], PrimeQ[4*# + 1] && PrimeQ[4*# + 3] && PrimeQ[4*# + 7] && PrimeQ[4*# + 9] && PrimeQ[4*# + 13] &]
    Select[Range[5*10^6], And @@ PrimeQ /@ ({1, 3, 7, 9, 13} + 4 #) &]
  • PARI
    for(n=1,10^7, if( isprime(4*n + 1) && isprime(4*n + 3) &&isprime(4*n + 7) &&isprime(4*n + 9) &&isprime(4*n + 13), print1(n,", ")))
    

A337491 Numbers k such that exactly one of 2*k + 3 and 4*k + 3 is prime.

Original entry on oeis.org

8, 11, 13, 16, 22, 26, 28, 29, 31, 35, 37, 38, 41, 43, 44, 50, 53, 56, 59, 64, 65, 68, 70, 73, 74, 76, 80, 85, 86, 88, 91, 97, 98, 107, 109, 112, 113, 116, 118, 121, 122, 125, 127, 133, 134, 136, 137, 139, 142, 145, 146, 149, 151, 152, 155, 160, 161, 167, 170
Offset: 1

Views

Author

K. D. Bajpai, Aug 29 2020

Keywords

Comments

Integers that are in A067076 or in A095278, but not in both. - Michel Marcus, Aug 29 2020

Examples

			a(1) = 8 is a term because 2*8 + 3 = 19 is a prime; but 4*8 + 3 = 35 = (5*7) is a composite number.
a(4) = 16 is a term because 2*16 + 3 = 35 = (5*7) is a composite number; but 4*16 + 3 = 67  is a prime.
a(6) = 26 is a term because 2*26 + 3 = 55 = (5*11) is a composite number; but 4*26 + 3 = 107  is a prime.
		

Crossrefs

Programs

  • Maple
    A337491:=n->`if`((isprime(2*n+3) xor isprime(4*n+3)), n, NULL): seq(A337491(n), n=1..500);
  • Mathematica
    Select[Range[0, 250], Xor[PrimeQ[2 # + 3], PrimeQ[4 # + 3]] &]
    Select[Range[200],Total[Boole[PrimeQ[{2,4}#+3]]]==1&] (* Harvey P. Dale, Jan 26 2023 *)
  • PARI
    isok(k) = bitxor(isprime(2*k+3), isprime(4*k+3)); \\ Michel Marcus, Aug 29 2020
Previous Showing 21-29 of 29 results.