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 1-3 of 3 results.

A093738 Number of pairs of consecutive prime (p,q) with q-p=6 and q < 10^n.

Original entry on oeis.org

0, 7, 44, 299, 1940, 13549, 99987, 768752, 6089791, 49392723, 408550278, 3435528229, 29289695650, 252672394234, 2201981901415, 19360330918473, 171550299264139, 1530609037414453
Offset: 1

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Author

Enoch Haga, Apr 15 2004

Keywords

Comments

Note that one has to be careful to distinguish between pairs of consecutive primes (p,q) with q-p = 6 (A031924), and pairs of primes (p,q) with q-p = 6 (A023201). Here we consider the former, whereas A080841 considers the latter. - N. J. A. Sloane, Mar 07 2021

Examples

			a(2) = 7 because there are 7 prime gaps of 6 below 10^2.

Links

Crossrefs

Cf. A007508, A080841, A093737, A093739.
See also A023201, A031924.

Programs

  • Mathematica
    Accumulate@ Array[Count[Differences@ Prime@ Range[PrimePi[10^(# - 1) + 1], PrimePi[10^# - 1]], 6] &, 8] (* Michael De Vlieger, Apr 09 2021 *)
  • UBASIC
    20 N=1:dim T(34); 30 A=nxtprm(N); 40 N=A; 50 B=nxtprm(N); 60 D=B-A; 70 for x=2 to 34 step 2; 80 if D=X and B<10^2+1 then T(X)=T(X)+1; 90 next X; 100 if B>10^2+1 then 140; 110 B=A; 120 N=N+1; 130 goto 30; 140 for x=2 to 34 step 2; 150 print T(X);, 160 next (This program simultaneously finds values from 2 to 34 -- if gap=2 add 1-- adjust lines 80 and 100 for desired 10^n)

Extensions

a(10)-a(13) from Washington Bomfim, Jun 22 2012
a(14)-a(18) from S. Herzog's website added by Giovanni Resta, Aug 14 2018

A080840 Number of cousin primes < 10^n.

Original entry on oeis.org

1, 8, 41, 203, 1216, 8144, 58622, 440258, 3424680, 27409999, 224373161, 1870585459, 15834656003, 135779962760, 1177207270204
Offset: 1

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Author

Jason Earls, Mar 28 2003

Keywords

Comments

The corresponding numbers for twin primes and sexy primes are in A007508 and A080841, the greater of twin primes, cousin primes and sexy primes are in A006512, A046132 and A046117 respectively.
In this sequence, only the upper member of each prime cousin pair is counted. See A152052 for the variant where only the lower member is counted. - James Rayman, Jan 17 2021

Links

Crossrefs

Cf. A007508, A080841, A006512, A046132, A046117, A152052, A152127.

Programs

  • PARI
    {c=0; p=5; for(n=1,9, while(p<10^n,if(isprime(p-4),c++); p=nextprime(p+1)); print1(c,","))}

Extensions

a(8) and a(9) from Klaus Brockhaus, Mar 30 2003
More terms from R. J. Mathar, Aug 05 2007
a(13)-a(15) from Martin Ehrenstein, Sep 03 2021

A341843 Number of sexy consecutive prime pairs below 2^n.

Original entry on oeis.org

0, 0, 0, 0, 1, 4, 7, 13, 25, 45, 80, 136, 251, 443, 784, 1377, 2420, 4312, 7756, 14106, 25554, 46776, 85774, 157325, 290773, 538520, 1000321, 1861364, 3473165, 6493997, 12167342, 22851920, 42987462, 81018661, 152945700, 289206487, 547722346, 1038786862
Offset: 1

Views

Author

Artur Jasinski, Feb 21 2021

Keywords

Comments

a(n) is the number of pairs of consecutive sexy primes {A023201, A046117} less than 2^n.
For each n from 9 through 48, the most frequently occurring difference between consecutive primes is 6. On p. 108 of the article by Odlyzko et al., the authors estimate that around n=117, the jumping champion (i.e., the most frequently occurring difference between consecutive primes) becomes 30, and around n=1412 it becomes 210. Successive jumping champions are conjecturaly the primorial numbers A002110.
Data for n >= 15 taken from Marek Wolf's prime gaps computation.
For the number of pairs of consecutive primes below 10^n having a difference of 6, see A093738.
For the number of sexy primes less than 10^n, see A080841.
There are 8 known cases in which a power of 2 falls between the members of the sexy consecutive prime pair (see A220951), but if a pair (p, p+6) is such that p < 2^n < p+6, that pair is not counted in a(n).

Examples

			a(6)=4 because 2^6=64 and we have 4 sexy consecutive prime pairs less than 64: {23,29}, {31,37}, {47,53}, {53,59}.

Links

Crossrefs

Cf. A002110, A023201, A046117, A080841, A098428, A104037, A220951, A226068, A227346.

Programs

  • Mathematica
    pp = {}; Do[kk = 0; Do[If[Prime[m + 1] - Prime[m] == 6, kk = kk + 1], {m, 2, PrimePi[2^n] - 1}]; AppendTo[pp, kk], {n, 4, 20}]; pp
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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