The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A098428 Number of sexy prime pairs (p, p+6) with p <= n. 6
 0, 0, 0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,7 COMMENTS Since there are 2 congruence classes of sexy prime pairs, (-1, -1) (mod 6) and (+1, +1) (mod 6), the number of sexy prime pairs up to n is the sum of the number of sexy prime pairs for each class, expected to be asymptotically the same for both (with the expected Chebyshev bias against the quadratic residue class (+1, +1) (mod 6), which doesn't affect the asymptotic distribution among the 2 classes). - Daniel Forgues, Aug 05 2009 LINKS Daniel Forgues, Table of n, a(n) for n=1..99994 Eric Weisstein's World of Mathematics, Sexy Primes FORMULA a(n) = # { p in A023201 | p <= n } = number of elements in intersection of A023201 and [1,n]. - M. F. Hasler, Jan 02 2020 EXAMPLE The first sexy prime pairs are: (5,11), (7,13), (11,17), (13,19), ... therefore the sequence starts: 0, 0, 0, 0, 1, 1, 2, 2, 2, 2, 3, 3, 4, ... MATHEMATICA Accumulate[Table[If[PrimeQ[n]&&PrimeQ[n+6], 1, 0], {n, 100}]] (* Harvey P. Dale, Feb 08 2015 *) PROG (PARI) apply( {A098428(n, o=2, q=o, c)=forprime(p=1+q, n+6, (o+6==p)+((o=q)+6==q=p) && c++); c}, [1..99]) \\ M. F. Hasler, Jan 02 2020 [#[p:p in PrimesInInterval(1, n)| IsPrime(p+6)]:n in [1..100]]; // Marius A. Burtea, Jan 03 2020 CROSSREFS Cf. A023201, A046117, A098424, A071538, A098429. Sequence in context: A209082 A257684 A098424 * A023193 A096605 A189671 Adjacent sequences:  A098425 A098426 A098427 * A098429 A098430 A098431 KEYWORD nonn AUTHOR Reinhard Zumkeller, Sep 07 2004 EXTENSIONS Edited by Daniel Forgues, Aug 01 2009, M. F. Hasler, Jan 02 2020 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified February 27 13:18 EST 2020. Contains 332306 sequences. (Running on oeis4.)