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a(n) = n multiplied by its smallest prime factor; a(1) = 1.
7

%I #17 Jun 30 2022 05:57:42

%S 1,4,9,8,25,12,49,16,27,20,121,24,169,28,45,32,289,36,361,40,63,44,

%T 529,48,125,52,81,56,841,60,961,64,99,68,175,72,1369,76,117,80,1681,

%U 84,1849,88,135,92,2209,96,343,100,153,104,2809,108,275,112,171,116,3481,120,3721,124,189,128,325,132,4489,136,207

%N a(n) = n multiplied by its smallest prime factor; a(1) = 1.

%H Antti Karttunen, <a href="/A285109/b285109.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A020639(n) * n.

%F Other identities. For all n >= 1:

%F a(A285100(n)) = A065642(A285100(n)). [Agrees with A065642 on all terms of A285100, but not on any other points.]

%t a[n_] := n * FactorInteger[n][[1, 1]]; Array[a, 100] (* _Amiram Eldar_, Jun 30 2022 *)

%o (Scheme) (define (A285109 n) (* (A020639 n) n))

%o (PARI) a(n)=if(n==1, 1, n*factor(n)[1,1]); \\ _Joerg Arndt_, Oct 27 2021

%Y Cf. A005117, A020639, A032742, A253560, A285100.

%Y Differs from A065642 for the first time at n=12. See A284342 for all the differing points.

%K nonn

%O 1,2

%A _Antti Karttunen_, Apr 19 2017