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.
%I A097228 #19 Mar 03 2024 12:24:17
%S A097228 27,38,127,138,289,298,1127,1138,1289,1298,11127,11138,11289,11298,
%T A097228 111127,111138,111289,111298,1111127,1111138,1111289,1111298,11111127,
%U A097228 11111138,11111289,11111298,111111127,111111138,111111289,111111298
%N A097228 Numbers n such that the product of digits of n equals the concatenation of pi(d)'s where d runs through the digits of n.
%C A097228 This sequence is infinite because if n is in the sequence then the number with an arbitrary number of 1's in front of n is also in the sequence. Are 27, 38, 289 and 298 the only nontrivial terms (i.e., terms whose first digit is not 1) in this sequence? The next term is greater than 3*10^8.
%C A097228 There are no more nontrivial terms; i.e., all terms in the sequence are 27, 38, 289, 298 prepended with zero or more 1's. To see this, note that a nontrivial term must have at most 21 digits since 9^22 < 10^21, i.e., has 21 digits. Searching through all numbers in A009994 of at most 21 digits that do not start with 1 shows that there are no more nontrivial terms. - _Chai Wah Wu_, Aug 10 2017
%H A097228 Chai Wah Wu, <a href="/A097228/b097228.txt">Table of n, a(n) for n = 1..1000</a>
%H A097228 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (0, 0, 0, 11, 0, 0, 0, -10).
%F A097228 From _Chai Wah Wu_, Aug 10 2017: (Start)
%F A097228 a(n) = 11*a(n-4) - 10*a(n-8) for n > 10.
%F A097228 G.f.: x*(-1600*x^9 - 1620*x^8 - 380*x^7 - 270*x^6 - 120*x^5 - 8*x^4 + 138*x^3 + 127*x^2 + 38*x + 27)/(10*x^8 - 11*x^4 + 1). (End)
%e A097228 298 is in the sequence because 2*9*8 = 144 = concatenate(pi(2), pi(9), pi(8)) = concatenate(1, 4, 4).
%t A097228 h[a_]:=(v1={};Do[l=Length[a];v1=Join[v1, IntegerDigits[a[[n]]]], {n, l}]; FromDigits[v1]);v={};Do[h1=IntegerDigits[n];l=Length[h1]; p=Product[h1[[k]], {k, l}];s=Sum[h1[[k]], {k, l}];If[p>0&& p==h[PrimePi[h1]], v=Append[v, n];Print[v]], {n, 300000000}]
%t A097228 LinearRecurrence[{0,0,0,11,0,0,0,-10},{27,38,127,138,289,298,1127,1138,1289,1298},30] (* _Harvey P. Dale_, Jan 01 2019 *)
%o A097228 (Python)
%o A097228 from __future__ import division
%o A097228 A097228_list = [27,38] + [1000*(10**k-1)//9+d for k in range(20) for d in [127,138,289,298]] # _Chai Wah Wu_, Aug 10 2017
%Y A097228 Cf. A097227.
%K A097228 base,nonn
%O A097228 1,1
%A A097228 _Farideh Firoozbakht_, Aug 15 2004