A046407 Odd numbers with exactly 5 distinct palindromic prime factors.

116655, 151305, 174405, 209055, 220605, 361515, 407715, 430815, 442365, 839685, 874335, 908985, 920535, 1061445, 1072995, 1389255, 1601355, 1919505, 2025555, 2077005, 2183115, 2489655, 2516415, 2627205, 2869755, 3016365, 3028305

Offset

1,1

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

N:= 10^7; # for terms <= N
PP:= NULL:
for d from 1 to length(N)/2 do
  for x from 10^(d-1) to 10^d-1 do
    y:= x*10^(d-1) + rev(floor(x/10));
    if isprime(y) then PP:= PP, y fi;
  od;
  if d = 1 then PP:= PP, 11 fi;
od:
PP:= [PP][2..-1]:
Res:= NULL:
for i1 from 1 to nops(PP) do
     v1:= PP[i1];
     if v1*3*5*7*11 > N then break fi;
     for i2 from 1 to i1-1 do
       v2:= v1*PP[i2];
       if v2*3*5*7 > N then break fi;
       for i3 from 1 to i2-1 do
         v3:= v2*PP[i3];
         if v3 * 3*5 > N then break fi;
         for i4 from 1 to i3-1 do
           v4:= v3*PP[i4];
           if v4* 3 > N then break fi;
           for i5 from 1 to i4-1 do
             v:= v4*PP[i5];
             if v > N then break fi;
             Res:= Res, v
od od od od od:
sort([Res]); # Robert Israel, Mar 14 2024

Crossrefs

Cf. A046318, A046375.

Sequence in context: A206471 A172783 A252886 * A156417 A156865 A233681

Adjacent sequences: A046404 A046405 A046406 * A046408 A046409 A046410

Keyword

nonn,base

Author

Patrick De Geest, Jun 15 1998

Extensions

Offset corrected by Robert Israel, Mar 14 2024

Status

approved