login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A194830 Odd numbers for which the number of ways to express them as 2*p+q, p,q primes, is a new record. 4

%I

%S 7,9,17,33,45,51,75,93,105,135,153,165,225,273,285,315,405,465,495,

%T 525,735,765,945,1155,1365,1785,1995,2145,2415,2625,3045,3255,3465,

%U 3885,4095,4305,4725,4935,5145,5355,5565,5775,6405,6825,7665,8085,8925,9555

%N Odd numbers for which the number of ways to express them as 2*p+q, p,q primes, is a new record.

%C 2*(positions of records in A046927)+1. The corresponding new record number of representations is given in A194831.

%D See A046927.

%H Hugo Pfoertner, <a href="/A194830/b194830.txt">Table of n, a(n) for n = 1..322</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/LevysConjecture.html">Levy's Conjecture</a>

%e a(3)=17, because it can be represented in A194831(3)=4 different ways (17=2*2+13=2*3+11=2*5+7=2*7+3), whereas all smaller odd numbers can only be represented in a smaller number of ways.

%t ways[n_] := ways[n] = (w = 0; Do[ p = 2k + 1; q = n - k; If[PrimeQ[p] && PrimeQ[q], w++], {k, 1, n}]; w); record = 0; A194830 = Reap[Do[If[ways[n] > record, record = ways[n]; Print["2n+1 = ", 2n + 1, " record = ", record]; Sow[{ways[n], 2n + 1}]], {n, 0, 12000}]][[2, 1]][[All, 2]] (* _Jean-Fran├žois Alcover_, Dec 05 2012 *)

%Y Cf. A046927, A194831 (size of records).

%K nonn

%O 1,1

%A _Hugo Pfoertner_, Sep 12 2011

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 17 23:13 EDT 2022. Contains 356204 sequences. (Running on oeis4.)