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 1-6 of 6 results.

A023203 Primes p such that p + 10 is also prime.

Original entry on oeis.org

3, 7, 13, 19, 31, 37, 43, 61, 73, 79, 97, 103, 127, 139, 157, 163, 181, 223, 229, 241, 271, 283, 307, 337, 349, 373, 379, 409, 421, 433, 439, 457, 499, 547, 577, 607, 631, 643, 673, 691, 709, 733, 751, 787, 811, 829, 853, 877, 919, 937, 967, 1009, 1021, 1039, 1051
Offset: 1

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Author

Keywords

Comments

A subset of A002476. It appears that this is also a subset of A007645. The first few terms of A007645 that are not in this sequence are {67, 109, 151, 193, 199, 211, 277, 313, 331, 367, 397, 463, 487, 523, 541, 571, 601, 613, ...}. - Alexander Adamchuk, Aug 15 2006
The entries are all in A007645, because they cannot be of the form p = 3*j + 2. If they were, p + 10 = 3*j + 12 would be divisible by 3 and not prime. - R. J. Mathar, Oct 30 2009

Crossrefs

Different from A015916. Cf. A031928, A079033.

Programs

  • Magma
    [n: n in [0..1000] | IsPrime(n) and IsPrime(n+10)]; // Vincenzo Librandi, Nov 20 2010
    
  • Maple
    for p from 1 to 10000 do if isprime(p) and isprime(p+10) then print(p) end if end do # Matt C. Anderson, Aug 26 2022
  • Mathematica
    Select[Prime[Range[200]], PrimeQ[# + 10] &] (* Harvey P. Dale, Dec 14 2011 *)
  • PARI
    is(n)=isprime(n)&&isprime(n+10) \\ Charles R Greathouse IV, Jul 01 2013

Extensions

Revised by N. J. A. Sloane, Jan 29 2013
New name from Michel Marcus, Mar 04 2020

A092216 Primes of the form p + 12 where p is a prime.

Original entry on oeis.org

17, 19, 23, 29, 31, 41, 43, 53, 59, 71, 73, 79, 83, 101, 109, 113, 139, 149, 151, 163, 179, 191, 193, 211, 223, 239, 241, 251, 263, 269, 281, 283, 293, 349, 359, 379, 401, 409, 421, 431, 433, 443, 461, 479, 491, 499, 503, 521, 569, 599, 613, 619, 631, 643, 653
Offset: 1

Views

Author

Douglas Winston (douglas.winston(AT)srupc.com), Apr 02 2004

Keywords

Crossrefs

Programs

Formula

a(n) = 12 + A046133(n). - R. J. Mathar, Jun 21 2010

A140445 List of prime pairs of form p, p + 10.

Original entry on oeis.org

3, 13, 7, 17, 13, 23, 19, 29, 31, 41, 37, 47, 43, 53, 61, 71, 73, 83, 79, 89, 97, 107, 103, 113, 127, 137, 139, 149, 157, 167, 163, 173, 181, 191, 223, 233, 229, 239, 241, 251, 271, 281, 283, 293, 307, 317, 337, 347, 349, 359, 373, 383, 379, 389, 409, 419, 421
Offset: 1

Views

Author

Juri-Stepan Gerasimov, Jun 26 2008

Keywords

Crossrefs

Cf. A023203 (1st bisection), A092146 (2nd bisection).
Cf. prime pairs of the form (p, p+k): A077800 (k=2), A094343 (k=4), A156274 (k=6), A156320 (k=8), this sequence (k=10), A156323 (k=12), A140446 (k=14), A272815 (k=16), A156328 (k=18), A272816 (k=20), A140447 (k=22).

Programs

  • Maple
    i: 1: for k from 1 to 1200 do if isprim (k) and isprim (k+10) then a [ i ] : = k : a [ i + 1]: = k + 10 : i = i + 2 fi od : seq (a [ n ], n=1..i-1);
  • Mathematica
    Flatten[{#,#+10}&/@Select[Prime[Range[100]],PrimeQ[#+10]&]]  (* Harvey P. Dale, Apr 11 2011 *)

Extensions

Corrected by D. S. McNeil, Dec 10 2009

A206768 a(n) = smallest number k such that sigma(k-n) = sigma(k) - n, with k > n+1.

Original entry on oeis.org

3, 5, 5, 7, 7, 11, 81, 11, 11, 13, 13, 17, 4431, 17, 17, 19, 19, 23, 25, 23, 23, 29
Offset: 1

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Author

Paolo P. Lava, Jan 10 2013

Keywords

Comments

This sequence begins
3, 5, 5, 7, 7, 11, 81, 11, 11, 13, 13, 17, 4431, 17, 17, 19, 19, 23, 25, 23, 23, 29, ?, 29, ?, 29, 29, 31, 31, 37, ?, 37, 51, 37, 37, 41, 81, 41, 41, 43, 43, 47, ?, 47, 47, 53, ?, 53, 3364, 53, 53, 59, ?, 59, ?, 59, 59, 61, 61, 67, ?, 67, ?, 67, 67, 71, ?, 71, 71, 73, 73, 79, 91, 79, ?, 79, 79, 83, ?, 83, 83, 89, ?, 89, ?, 89, 89, 101, ?, 97, ?, 97, 125, 97, 97, 101, ?, 101, 101, 103, 103, 107... where the other missing terms (designated by "?") are > 10^6, if they exist.
For a given n, n being even, among the integers k satisfying the property sigma(k-n) = sigma(k)-n, we will find prime numbers p, such that p and p-n are primes. This is because in that case sigma(p-n) = (p-n)+1 = (p+1)-n = sigma(p)-n. For instance, when n is even, for n=2 to 14, a(n) is the first term of A006512, A046132, A046117, A092402, A092146, A092216, A098933. If we restrict to composite numbers, then see A084293. - Michel Marcus, Feb 16 2013
For the missing terms mentioned in first comment, a(n) is > 10^7. - Michel Marcus, Sep 21 2013

Examples

			a(13) = 4431 because 4431 is the minimum number for which sigma(4431-13) = sigma(4418)= 6771 and sigma(4431) - 13 = 6784 -13 = 6771.
a(19) = 25 because 25 is the minimum number for which sigma(25-19) = sigma(6) = 12 and sigma(25) - 19 = 31 -19 = 12.
		

Crossrefs

Cf. A015886.

Programs

  • Maple
    A206768:=proc(q)
    local k,n;
    for n from 1 to q do
      for k from n+1 to q do
      if sigma(-n+k)=sigma(k)-n then print(k); break; fi;
    od; od; end:
    A206768(1000000000);

A098933 Primes of the form p+14, where p is a prime.

Original entry on oeis.org

17, 19, 31, 37, 43, 61, 67, 73, 97, 103, 127, 151, 163, 181, 193, 211, 241, 271, 277, 283, 307, 331, 367, 373, 397, 433, 457, 463, 523, 571, 577, 601, 607, 613, 631, 661, 673, 691, 733, 757, 787, 811, 823, 853, 877, 967, 991, 997, 1033, 1063, 1117, 1123, 1201
Offset: 1

Views

Author

Douglas Winston (douglas.winston(AT)srupc.com), Oct 20 2004

Keywords

Crossrefs

Programs

  • PARI
    isok(n) = isprime(n) && isprime(n - 14) \\ Michel Marcus, Jul 17 2013

A140547 Primes p such that neither p - 10 nor p + 10 is prime.

Original entry on oeis.org

2, 5, 11, 59, 67, 101, 109, 131, 151, 179, 193, 197, 199, 211, 227, 257, 263, 269, 277, 311, 313, 331, 353, 367, 397, 401, 461, 463, 479, 487, 491, 503, 521, 523, 541, 563, 569, 571, 593, 599, 601, 613, 619, 647, 659, 661, 677, 727, 739, 757, 769, 773, 809
Offset: 1

Views

Author

Juri-Stepan Gerasimov, Jun 30 2008, Nov 07 2009

Keywords

Crossrefs

Programs

  • Mathematica
    Select[Prime[Range[140]],!PrimeQ[#+10]&&(!PrimeQ[#-10]||#<10)&] (* James C. McMahon, Jul 12 2025 *)

Extensions

Edited by Charles R Greathouse IV, Mar 25 2010
Showing 1-6 of 6 results.