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A085648 Brilliant numbers (A078972) whose digital sum is also brilliant.

%I A085648 #12 Nov 24 2020 16:38:43
%S A085648 4,6,9,15,121,253,361,437,451,473,527,671,703,799,851,901,923,979,
%T A085648 1003,1027,1067,1081,1139,1157,1207,1247,1261,1333,1513,1517,1643,
%U A085648 1711,2183,2291,2701,2813,3007,3403,3551,3589,3713,4307,4399,4489,5041,5063,5767
%N A085648 Brilliant numbers (A078972) whose digital sum is also brilliant.
%H A085648 Robert Israel, <a href="/A085648/b085648.txt">Table of n, a(n) for n = 1..10000</a>
%e A085648 7470269 is a term because 7470269 = 1249*5981 and 7+4+7+0+2+6+9 = 35 = 5*7.
%p A085648 isbril:= proc(n) local F;
%p A085648   F:= ifactors(n)[2];
%p A085648   (nops(F)=1 and F[1][2]=2) or (nops(F)=2 and F[1][2]=1 and F[2][2]=1 and ilog10(F[1][1])=ilog10(F[2][1]))
%p A085648 end proc:
%p A085648 R:= NULL:
%p A085648 for d from 1 to 2 do
%p A085648   if d = 1 then P:= [2,3,5,7]
%p A085648   else P:= select(isprime, [seq(i,i=10^(d-1)+1..10^d-1,2)])
%p A085648   fi;
%p A085648   R:= R, op(sort(select(t -> isbril(convert(convert(t,base,10),`+`)), [seq(seq(P[i]*P[j],j=1..i),i=1..nops(P))])))
%p A085648 od:
%p A085648 R; # _Robert Israel_, Nov 24 2020
%Y A085648 Cf. A078972.
%K A085648 base,nonn
%O A085648 1,1
%A A085648 _Amarnath Murthy_, _Jason Earls_, Jul 11 2003
%E A085648 Offset changed by _Robert Israel_, Nov 24 2020