%I #14 May 25 2019 02:35:03

%S 12,20,28,63,44,52,117,68,76,171,92,207,345,116,124,279,465,148,333,

%T 164,172,387,188,423,705,212,477,795,236,244,549,915,268,603,284,292,

%U 657,1095,316,711,332,747,1245,356,801,1335,1869,388

%N Smallest prime product p*q*r such that p + q + r = 2*n + 1.

%C From _Robert Israel_, May 24 2019: (Start)

%C If p is an odd prime, then a((p+3)/2) = 4*p.

%C If p > 2 is in A067774, then a((p+5)/2) = 9*p. (End)

%H Robert Israel, <a href="/A210968/b210968.txt">Table of n, a(n) for n = 3..10000</a>

%p N:= 100: # for a(3)..a(N)

%p P:= select(isprime, [2,seq(i,i=3..2*N+1,2)]): nP:= nops(P):

%p A:= Vector([infinity$(2*N+1)]):

%p for i from 1 to nP while 2*P[i] <= 2*N+1 do

%p p:= P[i];

%p for j from i to nP while p+P[j] <= 2*N+1 do

%p if p*P[j] < A[p+P[j]] then A[p+P[j]]:= p*P[j] fi

%p od od:

%p B:= Vector([infinity$(2*N+1)]):

%p for i from 1 to nP while 3*P[i] <= 2*N+1 do

%p p:= P[i];

%p for x from 4 to 2*N+1-p do

%p y:= p+x;

%p if A[x]*p < B[y] then B[y]:= A[x]*p fi

%p od od:

%p [seq(B[2*i+1],i=3..N)]; # _Robert Israel_, May 24 2019

%Y Cf. A067774, A210967.

%K nonn,look

%O 3,1

%A _Omar E. Pol_, Jun 29 2012