A194039 - OEIS

%I #11 Jan 11 2020 05:34:06

%S 1,1,11,1,27,1,86,66,83,1,123,146,300,1,227,1,504,416,363,1,724,486,

%T 912,1,627,1,1252,786,843,902,1544,1256,1864,1158,1227,1,2340,1820,

%U 1523,1,2582,1766,3490,1938,2027,2118,4499,2306,2403,2502,2603,2706

%N Sum of nonprime divisors of n^2 + 1.

%H Amiram Eldar, <a href="/A194039/b194039.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A023890(n^2 + 1). - R. J. Mathar, Aug 14 2011

%e a(3) = 11 because 3^2 + 1 =  10 with the divisors {1, 2, 5, 10}, and the sum of the nonprime divisors is 1 + 10 = 11.

%t Array[ Plus @@ (Select[ Divisors[#^2+1],(!PrimeQ[#])& ])&, 75 ]

%K nonn,easy

%O 1,3

%A _Michel Lagneau_, Aug 12 2011