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A171435 Product of odd prime factors < n, with multiplicity.

%I A171435 #6 Mar 27 2022 23:31:14
%S A171435 1,1,1,1,1,3,1,1,9,5,1,3,1,7,15,1,1,9,1,5,21,11,1,3,25,13,27,7,1,15,1,
%T A171435 1,33,17,35,9,1,19,39,5,1,21,1,11,45,23,1,3,49,25,51,13,1,27,55,7,57,
%U A171435 29,1,15,1,31,63,1,65,33,1,17,69,35,1,9,1,37,75,19,77,39,1,5,81,41,1,21,85
%N A171435 Product of odd prime factors < n, with multiplicity.
%C A171435 In this sequence p < n, but p^k with k>=2 may be equal to n.
%C A171435 a(n) = 1 iff n = 2^k, k >= 0 or n is prime;
%C A171435 1 < a(n) < n iff n is even composite and not a power of 2;
%C A171435 a(n) = n iff n is nonprime (unit or composite) odd.
%H A171435 Daniel Forgues, <a href="/A171435/b171435.txt">Table of n, a(n) for n=1..100000</a>
%F A171435 If A010051(n) = 1 [when n is a prime], then a(n) = 1, otherwise a(n) = A000265(n). - _Antti Karttunen_, Mar 27 2022
%o A171435 (PARI) A171435(n) = if(isprime(n), 1, n>>valuation(n,2)); \\ _Antti Karttunen_, Mar 27 2022
%Y A171435 Cf. A171487, A000265, A010051.
%K A171435 nonn
%O A171435 1,6
%A A171435 _Daniel Forgues_, Dec 09 2009
%E A171435 Edited by _Daniel Forgues_, Dec 10 2009