This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
1 is the empty product; 44 is in the list because 44 = 2 * 22, 484 is in the list because 484 = 22 * 22.
M:= 10^8:
S:= {1}:
for d from 1 to ilog10(M) do
x:= 2/9*(10^d-1); T:= {}:
for s in S do
T:= T union {seq(s*x^i,i=1..floor(log[x](M/s)))};
od;
S:= S union T;
od:
sort(convert(S,list)); # Robert Israel, Dec 05 2024
1 = empty product; 99 = 3 * 33; 1089 = 33 * 33; 999 = 3 * 333.
M:= 10^8: # for terms <= M
S:= {1}:
for d from 1 to ilog10(M) do
x:= 3/9*(10^d-1); T:= {}:
for s in S do
T:= T union {seq(s*x^i,i=1..floor(log[x](M/s)))};
od;
S:= S union T;
od:
sort(convert(S,list)); # Robert Israel, Dec 05 2024
M:= 10^6: # for terms <= M
S:= {1}:
for d from 1 to ilog10(M) do
x:= 4/9*(10^d-1); T:= {}:
for s in S do
T:= T union {seq(s*x^i,i=1..floor(log[x](M/s)))};
od;
S:= S union T;
od:
sort(convert(S,list)); # Robert Israel, Dec 05 2024
1 = the empty product; 5 = 5; 125 = 5 * 5 * 5; 275 = 5 * 55; 2775 = 5 * 555.
216 = 6 * 6 * 6; 396 = 6 * 66; 3996 = 6 * 666.
Module[{upto=3*10^6,sevs=Table[FromDigits[PadRight[{},n,7]],{n,7}]},Select[ Union[ Flatten[Table[Times@@@Tuples[sevs,i],{i,7}]]],#<=upto&]] (* Harvey P. Dale, Feb 10 2015 *)
ns=Table[10^i-1,{i,7}]; Take[Union[Join[ns, Flatten[Table[Times@@@Tuples[ns,x], {x,2,8}]]]],50] (* Harvey P. Dale, Jan 19 2011 *)
nMax=10^7; ns=Table[10^i-1, {i,Floor[Log[10,nMax]]}]; u={1}; Do[While[u2=Union[u, Select[i*u, # <= nMax&]]; u != u2, u=u2], {i,ns}]; Rest[u]
ok[n_, w_: {}] := n <= 1 || AnyTrue[ Divisors@ n, ! MemberQ[w, #] && PalindromeQ[#] && ok[n/#, Append[w, #]] &]; Select[Range[0, 140], ok] (* Giovanni Resta, Apr 15 2020 *)
Comments