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 A278229 #13 Nov 22 2016 21:48:34
%S A278229 2,2,4,2,6,4,6,2,12,6,2,2,16,6,6,30,12,4,6,6,6,2,30,6,2,6,6,6,6,36,6,
%T A278229 12,30,2,24,6,2,12,12,30,30,4,6,30,6,2,2,6,6,2,30,12,6,6,24,60,6,2,6,
%U A278229 30,6,60,2,24,16,6,2,2,60,6,30,6,2,6,2,60,30,6,12,6,24,4,30,6,2,30,30,6,6,12,6,30,6,12,2,30,12,6,30,6,2,30,72,6,6,2,30,30
%N A278229 Least number with the prime signature of 2*prime(n) - 1.
%H A278229 Antti Karttunen, <a href="/A278229/b278229.txt">Table of n, a(n) for n = 1..10000</a>
%F A278229 a(n) = A046523(A076274(n)) = A046523((2*A000040(n))-1).
%t A278229 Table[Times @@ MapIndexed[(Prime@ First@ #2)^#1 &, #] &@ If[Length@ # == 1 && #[[1, 1]] == 1, {0}, Reverse@ Sort@ #[[All, -1]]] &@ FactorInteger[ 2 Prime@ n - 1], {n, 120}] (* _Michael De Vlieger_, Nov 21 2016 *)
%o A278229 (Scheme) (define (A278229 n) (A046523 (+ -1 (* 2 (A000040 n)))))
%Y A278229 Cf. A000040, A046523, A076274.
%Y A278229 Cf. A137288 (positions of 2's), A005382.
%Y A278229 Cf. also A278227, A278228, A278230.
%K A278229 nonn
%O A278229 1,1
%A A278229 _Antti Karttunen_, Nov 19 2016