cp's OEIS Frontend

A046407 Odd numbers with exactly 5 distinct palindromic prime factors.

%I A046407 #10 Mar 14 2024 19:40:48
%S A046407 116655,151305,174405,209055,220605,361515,407715,430815,442365,
%T A046407 839685,874335,908985,920535,1061445,1072995,1389255,1601355,1919505,
%U A046407 2025555,2077005,2183115,2489655,2516415,2627205,2869755,3016365,3028305
%N A046407 Odd numbers with exactly 5 distinct palindromic prime factors.
%H A046407 Robert Israel, <a href="/A046407/b046407.txt">Table of n, a(n) for n = 1..10000</a>
%p A046407 N:= 10^7; # for terms <= N
%p A046407 PP:= NULL:
%p A046407 for d from 1 to length(N)/2 do
%p A046407   for x from 10^(d-1) to 10^d-1 do
%p A046407     y:= x*10^(d-1) + rev(floor(x/10));
%p A046407     if isprime(y) then PP:= PP,y fi;
%p A046407   od;
%p A046407   if d = 1 then PP:= PP, 11 fi;
%p A046407 od:
%p A046407 PP:= [PP][2..-1]:
%p A046407 Res:= NULL:
%p A046407 for i1 from 1 to nops(PP) do
%p A046407      v1:= PP[i1];
%p A046407      if v1*3*5*7*11 > N then break fi;
%p A046407      for i2 from 1 to i1-1 do
%p A046407        v2:= v1*PP[i2];
%p A046407        if v2*3*5*7 > N then break fi;
%p A046407        for i3 from 1 to i2-1 do
%p A046407          v3:= v2*PP[i3];
%p A046407          if v3 * 3*5 > N then break fi;
%p A046407          for i4 from 1 to i3-1 do
%p A046407            v4:= v3*PP[i4];
%p A046407            if v4* 3 > N then break fi;
%p A046407            for i5 from 1 to i4-1 do
%p A046407              v:= v4*PP[i5];
%p A046407              if v > N then break fi;
%p A046407              Res:= Res, v
%p A046407 od od od od od:
%p A046407 sort([Res]); # _Robert Israel_, Mar 14 2024
%Y A046407 Cf. A046318, A046375.
%K A046407 nonn,base
%O A046407 1,1
%A A046407 _Patrick De Geest_, Jun 15 1998
%E A046407 Offset corrected by _Robert Israel_, Mar 14 2024