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 A072963 #12 Jan 10 2020 05:23:48
%S A072963 1,1,3,1,5,3,7,1,9,5,11,3,13,7,15,1,17,9,19,5,21,11,1,3,25,13,27,7,29,
%T A072963 15,31,1,33,17,35,9,1,19,39,5,41,21,43,11,45,1,1,3,49,25,51,13,1,27,
%U A072963 55,7,57,29,59,15,61,31,63,1,65,33,1,17,3,35,71,9,73,1,75,19,77,39,1,5,81
%N A072963 In prime factorization of n replace all single (i.e., non-twin) primes with 1.
%C A072963 a(a(n)) = a(n).
%H A072963 Amiram Eldar, <a href="/A072963/b072963.txt">Table of n, a(n) for n = 1..10000</a>
%F A072963 Multiplicative with a(p) = (if p+2 or p-2 is prime then p else 1), p prime.
%e A072963 a(92) = a(2*2*23) = 1; a(93) = a(3*31) = 3*31 = 93.
%t A072963 f[p_, e_] := If[!Or @@ PrimeQ[p + {-2, 2}], 1, p^e]; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 81] (* _Amiram Eldar_, Jan 10 2020 *)
%Y A072963 Cf. A007510, A000040.
%K A072963 nonn,mult
%O A072963 1,3
%A A072963 _Reinhard Zumkeller_, Aug 20 2002