cp's OEIS Frontend

A237992 Numbers which can be decomposed as p*q + q*r + r*p (where p < q < r are distinct primes) in more ways than any smaller number.

%I A237992 #30 Nov 07 2024 08:31:49
%S A237992 31,71,151,191,311,1031,1991,3191,5351,5591,10391,15791,17111,27191,
%T A237992 31391,35591,42311,50951,70391,93551,107159,117911,119831,126551,
%U A237992 166871,180311,191831,216191,255191,259871,327071,366791,435431,465911,514751,576551,599231,631991
%N A237992 Numbers which can be decomposed as p*q + q*r + r*p (where p < q < r are distinct primes) in more ways than any smaller number.
%C A237992 Records in A238403.
%e A237992 71 = 3*5 + 3*7 + 5*7 = 2*3 + 2*13 + 3*13 can be written in two ways, while smaller numbers can be written in at most one way.
%o A237992 (PARI) do(n)=my(v=vectorsmall(n),r); forprime(r=5,(n-6)\5, forprime(q=3, min((n-2*r)\(r+2),r-2), my(S=q+r,P=q*r); forprime(p=2,min((n-P)\S,q-1), v[p*S+P]++))); for(i=1,#v,if(v[i]>r,r=v[i];print1(i", ")))
%Y A237992 Cf. A238403, A087053, A238397.
%K A237992 nonn
%O A237992 1,1
%A A237992 _Charles R Greathouse IV_, Feb 26 2014