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 A281189 #18 Feb 01 2017 14:11:41
%S A281189 15,85,57,85,1111,185,4119,4369,489,451,13315,679,26533,985,1057,1285,
%T A281189 179503,1387,82311,2005,2649,2047,4663957,2509,2761,3385,3097,3277,
%U A281189 243895,4207,16246817,4369,4577,471651,5401,5629,607839,466429,483731,6817,1009273,10587,1132547,8119,8401,798731,990583,9809,1411791,1062517
%N A281189 a(n) is the first composite number having the same base-(2n) digits as its prime factors (with multiplicity), excluding zero digits (or 0 if no such composite number exists).
%C A281189 Bisection of A278981.
%C A281189 Conjecture: a(n) always exceeds 0.
%C A281189 If a(n) = 0 then it must be the case that there exists no more than one prime of the form (2n)^m + 1. Otherwise, the product of two such primes would satisfy the condition of A278981 in base 2n.
%C A281189 Records: 15, 85, 1111, 4119, 4369, 13315, 26533, 179503, 4663957, 16246817, 75927167, 120872069, 335192766, ..., .
%C A281189 a(76) > 2^27.
%H A281189 Ely Golden and Robert G. Wilson v, <a href="/A281189/b281189.txt">Table of n, a(n) for n = 1..75</a>
%F A281189 a(n) = A278981(2n).
%e A281189 a(2) = A278981(4) since 85 is the least composite number which satisfies the criterion of A278981.
%t A281189 g[n_] := g[n] = Flatten[ Table[#[[1]], {#[[2]]}] & /@ FactorInteger@ n]; f = Compile[{{b, _Integer}}, Block[{c = b^2}, While[ PrimeQ@ c || DeleteCases[ Sort[ IntegerDigits[c, b]], 0] != DeleteCases[ Sort[ Flatten[ IntegerDigits[ g[c], b]]], 0], c++]; c]]; Table[ f[b], {b, 2, 80, 2}]
%Y A281189 Cf. A278981, A280270.
%K A281189 base,nonn
%O A281189 1,1
%A A281189 _Ely Golden_ and _Robert G. Wilson v_, Jan 16 2017