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.
A000040(471) ....... = 3343 A000040(3570) ...... = 33343 A000040(28674) ..... = 333433 A000040(28743) ..... = 334333 A000040(13077233344) = 333333433343
[p: p in PrimesUpTo(43444433) | Set(Intseq(p)) subset [3,4]]; // Bruno Berselli, Jul 27 2012
Flatten[Table[Select[FromDigits/@Tuples[{3,4},n],PrimeQ],{n,8}]] (* Vincenzo Librandi, Jul 27 2012 *)
[p: p in [3..33333333343 by 10] | (p mod 100 eq 33 or p mod 100 eq 43) and IsPrime(p) and Position(IntegerToString(p), IntegerToString(3)) eq 1 and Set(Intseq(p)) subset [3, 4] and not IntegerToString(44) in IntegerToString(p)];
S:= {}:
for n from 3 to 16 do
for k from 1 to floor((n-1)/2) do
for r in combinat:-choose(n-1-k,k) do
L:=subsop(seq(t=(3,4),t=r),[3$(n-k)]);
x:= add(L[i]*10^(n-i),i=1..n);
if isprime(x) then S:= S union {x} fi
od od od:
sort(convert(S,list)); # Robert Israel, Mar 15 2016
Select[Flatten[Table[FromDigits/@Select[Tuples[{3,4},n],SequenceCount[ #,{3,4,3},Overlaps->True]==Count[#,4]&],{n,3,11}]],PrimeQ]//Sort (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Sep 17 2016 *)
a(5)=471 because A020461(5)=3343 and A000040(471)=3343, the 471st prime number.
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