A081313 - OEIS

%I #15 May 02 2022 16:18:38

%S 4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,25,26,27,29,30,

%T 31,32,33,34,35,37,38,39,40,41,43,44,45,46,47,49,50,51,53,55,56,57,59,

%U 61,62,63,64,65,67,68,69,70,71,73,74,75,76,77,79,80,81,82,83,84,85,86

%N Numbers having more than one representation as sum of a prime and a 3-smooth number.

%H Reinhard Zumkeller, <a href="/A081313/b081313.txt">Table of n, a(n) for n = 1..10000</a>

%F A081308(a(n)) > 1.

%t nmax = 1000;

%t S = Select[Range[nmax], Max[FactorInteger[#][[All, 1]]] <= 3 &];

%t A081308[n_] := Count[TakeWhile[S, # < n &], s_ /; PrimeQ[n - s]];

%t Select[Range[nmax], A081308[#] > 1 &] (* _Jean-François Alcover_, Oct 13 2021 *)

%o (Haskell)

%o a081313 n = a081313_list !! (n-1)

%o a081313_list = filter ((> 1) . a081308) [1..]

%o -- _Reinhard Zumkeller_, Jul 04 2012

%Y Cf. A000040, A003586, A081308, A081312.

%Y Subsequence of A081311.

%K nonn

%O 1,1

%A _Reinhard Zumkeller_, Mar 17 2003