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 A069177 #18 Sep 05 2023 01:44:31
%S A069177 1,1,2,2,4,2,2,4,2,4,2,4,4,2,8,8,16,2,2,8,4,2,2,8,4,4,2,4,4,8,2,16,4,
%T A069177 16,8,4,4,2,8,16,8,4,2,4,8,2,2,16,2,4,32,8,4,2,8,8,4,4,2,16,4,2,4,32,
%U A069177 16,4,2,32,4,8,2,8,8,4,8,4,4,8,2,32,2,8,2,8,64,2,8,8,8,8,8,4,4,2,8,32
%N A069177 Maximal power of 2 that divides Phi(n), or the size of the Sylow 2-subgroup of the group of units mod n.
%H A069177 Antti Karttunen, <a href="/A069177/b069177.txt">Table of n, a(n) for n = 1..10000</a>
%F A069177 a(n) = 2^A053574(n). Multiplicative with a(2^e) = 2^(e-1) and a(p^e) = power of 2 in prime factorization of p - 1 for an odd prime p. - _Vladeta Jovovic_, Apr 10 2002
%t A069177 Table[2^IntegerExponent[EulerPhi@ n, 2], {n, 96}] (* _Michael De Vlieger_, Aug 23 2017 *)
%o A069177 (Scheme) (define (A069177 n) (cond ((= 1 n) n) ((zero? (modulo n 4)) (* 2 (A069177 (/ n 2)))) ((even? n) (A069177 (/ n 2))) (else (* (A006519 (+ -1 (A020639 n))) (A069177 (A028234 n)))))) ;; (After Jovovic's multiplicative formula) - _Antti Karttunen_, Aug 22 2017
%o A069177 (PARI) a(n) = 2^valuation(eulerphi(n), 2); \\ _Amiram Eldar_, Sep 05 2023
%Y A069177 Cf. A000010, A006519, A053574, A023506.
%K A069177 nonn,easy,mult
%O A069177 1,3
%A A069177 Sharon Sela (sharonsela(AT)hotmail.com), Apr 09 2002
%E A069177 More terms from _Vladeta Jovovic_, Apr 10 2002