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.

Showing 1-8 of 8 results.

A030431 Primes of form 10n+3.

Original entry on oeis.org

3, 13, 23, 43, 53, 73, 83, 103, 113, 163, 173, 193, 223, 233, 263, 283, 293, 313, 353, 373, 383, 433, 443, 463, 503, 523, 563, 593, 613, 643, 653, 673, 683, 733, 743, 773, 823, 853, 863, 883, 953, 983, 1013, 1033, 1063, 1093, 1103, 1123, 1153, 1163, 1193
Offset: 1

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Author

Keywords

Comments

Also primes of form 5n+3.
Union of A132233, A132235, {3}. - Ray Chandler, Apr 07 2009
Primes p such that arithmetic mean of divisors of p^4 is an integer. There are 2 such sequences of primes, this one and A030430. - Ctibor O. Zizka, Oct 20 2009
5 is not quadratic residue of primes of this form. - Vincenzo Librandi, Jun 25 2014
Intersection of A000040 and A017305. - Iain Fox, Dec 30 2017

Crossrefs

Programs

Formula

a(n) = 10*A102338(n) + 3.

Extensions

Extended by Ray Chandler, Nov 07 2006

A007811 Numbers k for which 10k+1, 10k+3, 10k+7 and 10k+9 are primes.

Original entry on oeis.org

1, 10, 19, 82, 148, 187, 208, 325, 346, 565, 943, 1300, 1564, 1573, 1606, 1804, 1891, 1942, 2101, 2227, 2530, 3172, 3484, 4378, 5134, 5533, 6298, 6721, 6949, 7222, 7726, 7969, 8104, 8272, 8881, 9784, 9913, 10111, 10984, 11653, 11929, 12220, 13546, 14416, 15727
Offset: 1

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Author

N. J. A. Sloane and J. H. Conway, Mar 15 1996

Keywords

Crossrefs

Programs

  • Haskell
    a007811 n = a007811_list !! (n-1)
    a007811_list = map (pred . head) $ filter (all (== 1) . map a010051') $
       iterate (zipWith (+) [10, 10, 10, 10]) [1, 3, 7, 9]
    -- Reinhard Zumkeller, Jul 18 2014
    
  • Magma
    [n: n in [0..10000] | forall{10*n+r: r in [1,3,7,9] | IsPrime(10*n+r)}]; // Bruno Berselli, Sep 04 2012
    
  • Maple
    for n from 1 to 10000 do m := 10*n: if isprime(m+1) and isprime(m+3) and isprime(m+7) and isprime(m+9) then print(n); fi: od: quit
  • Mathematica
    Select[ Range[ 1, 10000, 3 ], PrimeQ[ 10*#+1 ] && PrimeQ[ 10*#+3 ] && PrimeQ[ 10*#+7 ] && PrimeQ[ 10*#+9 ]& ]
    Select[Range[15000], And @@ PrimeQ /@ ({1, 3, 7, 9} + 10#) &] (* Ray Chandler, Jan 12 2007 *)
  • PARI
    p=2;q=3;r=5;forprime(s=7,1e5,if(s-p==8 && r-p==6 && q-p==2 && p%10==1, print1(p", ")); p=q;q=r;r=s) \\ Charles R Greathouse IV, Mar 21 2013
    
  • Perl
    use ntheory ":all"; my @s = map { ($-1)/10 } sieve_prime_cluster(10,1e9, 2,6,8); say for @s; # _Dana Jacobsen, May 04 2017

Formula

a(n) = 3*A014561(n) + 1. - Zak Seidov, Sep 21 2009

A023238 Primes p such that 10*p + 3 is also prime.

Original entry on oeis.org

2, 5, 7, 11, 17, 19, 23, 29, 31, 37, 43, 59, 61, 67, 73, 101, 103, 109, 137, 149, 173, 191, 193, 197, 199, 211, 227, 229, 233, 239, 263, 269, 271, 283, 331, 337, 353, 359, 367, 373, 379, 383, 401, 409, 449, 467, 479, 499, 523, 541, 557, 569, 607, 613, 617, 647, 673, 683
Offset: 1

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Author

Keywords

Crossrefs

Cf. A023239.
Subsequence of A102338.

Programs

  • Magma
    [n: n in [0..1000] | IsPrime(n) and IsPrime(10*n+3)] // Vincenzo Librandi, Nov 20 2010
  • Maple
    A023238:=n->`if`(isprime(n) and isprime(10*n+3), n, NULL): seq(A023238(n), n=1..10^3); # Wesley Ivan Hurt, Sep 08 2016
  • Mathematica
    Select[Prime[Range[200]], PrimeQ[10# + 3] &] (* Alonso del Arte, Jun 24 2014 *)

A049508 Numbers k such that prime(k) == 3 (mod 10).

Original entry on oeis.org

2, 6, 9, 14, 16, 21, 23, 27, 30, 38, 40, 44, 48, 51, 56, 61, 62, 65, 71, 74, 76, 84, 86, 90, 96, 99, 103, 108, 112, 117, 119, 122, 124, 130, 132, 137, 143, 147, 150, 153, 162, 166, 170, 174, 179, 183, 185, 188, 191, 192, 196, 198, 200, 208, 213, 220, 224, 227, 231
Offset: 1

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Author

Keywords

Comments

The asymptotic density of this sequence is 1/4 (by Dirichlet's theorem). - Amiram Eldar, Mar 01 2021

Crossrefs

Programs

  • Mathematica
    Select[Range[240], Mod[Prime[ # ], 10] == 3 &] (* Ray Chandler, Nov 07 2006 *)

Formula

a(n) = A000720(A030431(n)). - Ray Chandler, Nov 07 2006

Extensions

Edited and extended by Ray Chandler, Nov 07 2006

A023269 Primes that remain prime through 2 iterations of function f(x) = 10x + 3.

Original entry on oeis.org

2, 7, 17, 19, 23, 37, 61, 67, 73, 101, 103, 173, 193, 233, 359, 383, 409, 479, 541, 557, 607, 613, 719, 809, 857, 997, 1013, 1033, 1109, 1117, 1237, 1297, 1361, 1459, 1531, 1549, 1699, 1823, 1871, 1979, 1999, 2069, 2131, 2161, 2347, 2377, 2399, 2447, 2663
Offset: 1

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Author

Keywords

Comments

Primes p such that 10*p+3 and 100*p+33 are also primes. - Vincenzo Librandi, Aug 04 2010

Crossrefs

Subsequence of A023238 and of A102338.

Programs

  • Magma
    [n: n in [1..100000] | IsPrime(n) and IsPrime(10*n+3) and IsPrime(100*n+33)] // Vincenzo Librandi, Aug 04 2010
  • Mathematica
    Select[Prime@ Range@ 400, Times @@ Boole@ PrimeQ@ Rest@ NestList[10 # + 3 &, #, 2] > 0 &] (* Michael De Vlieger, Sep 16 2016 *)
    Select[Prime[Range[500]],AllTrue[Rest[NestList[10#+3&,#,2]],PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Sep 03 2018 *)

A153403 Numbers n such that 10*n+3 is not prime.

Original entry on oeis.org

3, 6, 9, 12, 13, 14, 15, 18, 20, 21, 24, 25, 27, 30, 32, 33, 34, 36, 39, 40, 41, 42, 45, 47, 48, 49, 51, 53, 54, 55, 57, 58, 60, 62, 63, 66, 69, 70, 71, 72, 75, 76, 78, 79, 80, 81, 83, 84, 87, 89, 90, 91, 92, 93, 94, 96, 97, 99, 100
Offset: 1

Views

Author

Vincenzo Librandi, Dec 25 2008

Keywords

Examples

			Distribution of the terms in the following triangular array:
*;
*,*;
*,*,*;
*,*,6,*;
3,*,*,*,*;
*,*,*,*,14,*;
*,*,*,*,*,*,*;
*,*,*,15,*,*,*,*;
*,*,13,*,*,*,*,32,*;
6,*,*,*,*,27,*,*,*,*;
*,*,*,*,25,*,*,*,*,48,*; etc.
where * marks the non-integer values of (2*h*k + k + h - 1)/5 with n >= k >= 1. - _Vincenzo Librandi_, Jan 14 2013
		

Crossrefs

Cf. A102338.

Programs

A102915 Numbers n such that n3 is prime and n is a multiple of 10.

Original entry on oeis.org

0, 10, 50, 110, 130, 200, 220, 250, 280, 290, 320, 380, 400, 460, 470, 490, 500, 530, 550, 590, 620, 670, 680, 710, 760, 770, 880, 910, 920, 940, 980, 1010, 1030, 1090, 1100, 1150, 1190, 1220, 1250, 1270, 1300, 1310, 1390, 1430, 1450, 1580, 1610, 1660, 1670, 1690, 1720, 1790, 1850, 1880
Offset: 1

Views

Author

Parthasarathy Nambi, Mar 01 2005

Keywords

Examples

			If t=10, then t3 = 103 (prime).
If t=280, then t3 = 2803 (prime).
If t=490, then t3 = 4903 (prime).
		

Crossrefs

Cf. A102338.

Programs

  • Mathematica
    Select[10*Range[0,200],PrimeQ[10#+3]&] (* Harvey P. Dale, Mar 23 2015 *)

A126332 Numbers k such that 10k + 13 is prime.

Original entry on oeis.org

0, 1, 3, 4, 6, 7, 9, 10, 15, 16, 18, 21, 22, 25, 27, 28, 30, 34, 36, 37, 42, 43, 45, 49, 51, 55, 58, 60, 63, 64, 66, 67, 72, 73, 76, 81, 84, 85, 87, 94, 97, 100, 102, 105, 108, 109, 111, 114, 115, 118, 120, 121, 127, 129, 136, 141, 142, 144, 147, 148, 151, 153, 154, 157
Offset: 1

Views

Author

Parthasarathy Nambi, Mar 10 2007

Keywords

Examples

			For k = 100, 10*k + 13 = 1013 (prime).
		

Crossrefs

Programs

Formula

a(k) = A102338(k+1) - 1. - R. J. Mathar, Jul 08 2009
Showing 1-8 of 8 results.