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 1-4 of 4 results.

A137796 Prime numbers p such that p + 12 and p - 12 are primes.

Original entry on oeis.org

17, 19, 29, 31, 41, 59, 71, 101, 139, 151, 179, 211, 239, 251, 269, 281, 409, 421, 431, 479, 491, 619, 631, 739, 809, 941, 1009, 1021, 1051, 1289, 1291, 1439, 1459, 1471, 1499, 1511, 1571, 1609, 1709, 1721, 1789, 1889, 1901, 1999, 2099, 2141, 2281, 2411
Offset: 1

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Author

Keywords

Examples

			17 + 12 = 29 (a prime), 17 - 12 = 5 (a prime);
19 + 12 = 31 (a prime), 19 - 12 = 7 (a prime).
		

Crossrefs

Cf. A092216, A046133. Note that this is different from A137873.

Programs

  • Maple
    isA092216 := proc(n) RETURN(isprime(n) and isprime(n-12) ) ; end: isA046133 := proc(n) RETURN(isprime(n) and isprime(n+12) ) ; end: isA137796 := proc(n) RETURN(isA092216(n) and isA046133(n)) ; end: for i from 1 to 400 do if isA137796(ithprime(i)) then printf("%d,",ithprime(i)) ; fi ; od: # R. J. Mathar, May 03 2008
  • Mathematica
    a=12; Select[Table[Prime[n],{n,10^3}], PrimeQ[ #-a] && PrimeQ[ #+a] &]
  • PARI
    lista(nn) = forprime(p=2, nn, if (isprime(p-12) && isprime(p+12), print1(p, ", "))); \\ Michel Marcus, Oct 04 2015

Formula

A092216 INTERSECT A046133. - R. J. Mathar, May 03 2008

Extensions

Corrected and extended by R. J. Mathar, May 03 2008

A156323 List of prime pairs of the form (p, p+12).

Original entry on oeis.org

5, 17, 7, 19, 11, 23, 17, 29, 19, 31, 29, 41, 31, 43, 41, 53, 47, 59, 59, 71, 61, 73, 67, 79, 71, 83, 89, 101, 97, 109, 101, 113, 127, 139, 137, 149, 139, 151, 151, 163, 167, 179, 179, 191, 181, 193, 199, 211, 211, 223, 227, 239, 229, 241, 239, 251, 251, 263, 257
Offset: 1

Views

Author

Vincenzo Librandi, Feb 08 2009

Keywords

Examples

			For p=5, 5+12=17, (5,17); p=59, 59+12=71, (59,71)
		

Crossrefs

Programs

  • Mathematica
    Flatten[Select[{#,#+12}&/@Prime[Range[100]], PrimeQ[Last[#]]&]]  (* Harvey P. Dale, Mar 23 2011 *)

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
Showing 1-4 of 4 results.