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 A089174 #32 Aug 24 2023 10:11:12
%S A089174 2,3,7,11,13,17,19,23,37,41,59,73,101,137,157,239,257,271,547,2153,
%T A089174 2251,4649,7309,9091,19697,21683,94331,333667,928163,3324301,4403881,
%U A089174 7532639,8983031,10901027,1111211111,11195538763,139381546141,1102732004467
%N A089174 A nonsense sequence (not well-defined).
%C A089174 Previous name was: Unique prime factors in A007907 extended to modulo 10 (past 20 elements).
%C A089174 This sequence is finite based on the data given. Since the Mathematica code is the main source of information for this sequence the data and code match for the given digits = 30 component. Increasing digits to, say, 50, increases the number of terms for be factored in A007907 and increases the number of terms to be ordered. This gives more values of this sequence. Since the data is established this removes any more terms from being added, which makes it a finite sequence. - _G. C. Greubel_, Aug 17 2023
%e A089174 A007907 = {1, 11, 121, 1221, 12321, 123321, ...} which factor as {(1^1), (11^1), (11^2), (3^1, 11^1, 37^1), (3^2, 37^2), (3^1, 11^1, 37^1, 101^1), ...}. The list of the factors and their powers, flattened, begins as {1, 1, 11, 1, 11, 2, 3, 1, 11, 1, 37, 1, 3, 2, 37, 2, ...}. The list of ordered prime values begins as {2, 3, 7, 11, ...}.
%t A089174 digits=30;
%t A089174 f[m_]= Table[If[Floor[m/2]>=n, Mod[n, 10], Mod[m-n, 10]], {n,m}];
%t A089174 A007907= Table[Sum[f[m][[i]]*10^(i-1), {i,m}], {m, digits}];
%t A089174 c= Flatten[Table[FactorInteger[A007907[[n]]], {n, digits-1}]];
%t A089174 Rest@Union[Table[If[PrimeQ[c[[n]]], c[[n]], 1], {n, Dimensions[c][[1]]}]]
%Y A089174 Cf. A007907.
%K A089174 nonn,base,fini,less
%O A089174 1,1
%A A089174 _Roger L. Bagula_, Dec 07 2003
%E A089174 Edited by _G. C. Greubel_, Aug 17 2023