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%I #8 Aug 10 2019 04:54:39
%S 1,3,4,5,6,11,8,9,10,16,12,18,14,21,23,17,18,26,20,28,30,31,24,33,26,
%T 36,28,37,30,57,32,33,45,46,47,45,38,51,52,51,42,77,44,55,58,61,48,62,
%U 50,66,67,64,54,71,70,68,74,76,60,100,62,81,77,65,82,113,68,82,89,118,72
%N a(n) gives sum of number of common unitary divisors of n and m, where m runs from 1 to n.
%H Amiram Eldar, <a href="/A089912/b089912.txt">Table of n, a(n) for n = 1..10000</a>
%t udiv[n_] := Select[Divisors[n], GCD[#, n/#]==1 &]; a[n_] := Module[{d = udiv[n]}, Sum[Length[Intersection[d, udiv[k]]], {k,1,n}]]; Array[a, 100] (* _Amiram Eldar_, Aug 10 2019 *)
%o (PARI) a(n) = {sdivn = Set(); fordiv(n, d, if (gcd(d, n/d) == 1, sdivn = setunion(sdivn, Set(d)))); s = 0; for (m=1, n, sdivm = Set(); fordiv(m, d, if (gcd(d, m/d) == 1, sdivm = setunion(sdivm, Set(d)))); s += length(setintersect(sdivn, sdivm));); return (s);} \\ _Michel Marcus_, Jul 15 2013
%Y Cf. A034444, A034448.
%K easy,nonn
%O 1,2
%A _Naohiro Nomoto_, Jan 11 2004
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