A087747 Least number expressible as a sum of two distinct primes in exactly n ways.

5, 16, 24, 36, 48, 60, 78, 84, 90, 114, 144, 120, 168, 180, 234, 246, 288, 240, 210, 324, 300, 360, 474, 330, 528, 576, 390, 462, 480, 420, 570, 510, 672, 792, 756, 876, 714, 798, 690, 1038, 630, 1008, 930, 780, 960, 870, 924, 900, 1134, 1434, 840, 990, 1302, 1080, 1230, 1518

Offset: 1

Author

Lekraj Beedassy, Oct 02 2003

Keywords

• nonn

Examples

			a(2)=16 because we have 16=3+13=5+11, followed by 18=5+13=7+11; 20=3+17=7+13; 22=3+19=5+17; 26=3+23=7+19;...
		

Links

• Paolo P. Lava, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A117929.

Programs

Mathematica

Module[{nn=2000,ip},ip=Table[{n,Length[Select[IntegerPartitions[n,{2}], #[[1]]!=#[[2]]&&AllTrue[#,PrimeQ]&]]},{n,nn}];Table[SelectFirst[ip, #[[2]]==k&],{k,60}]][[All,1]] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jul 11 2020 *)

Formula

a(n) = min({m >= 1 : A117929(m) = n}). - Peter Munn, May 01 2023

Extensions

More terms from John Dethridge (jcd(AT)ms.unimelb.edu.au), Jan 08 2004

More terms from Hugo Pfoertner, Sep 23 2004

Reinserted a(18), a(19) and a(20) by Paolo P. Lava, May 26 2014