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Numbers that are the sum of their first k non-divisors for some k.
3

%I #21 Nov 23 2015 09:15:09

%S 5,8,12,51,56,85,87,105,132,164,224,249,280,321,324,343,357,363,366,

%T 405,427,428,553,583,591,618,638,654,689,699,820,918,978,1028,1045,

%U 1077,1144,1207,1261,1267,1268,1342,1377,1417,1477,1505,1517,1691,1692,1707,1758,1794,1805,1883,1927,2197,2322,2334,2384,2461,2481,2523,2525,2568

%N Numbers that are the sum of their first k non-divisors for some k.

%H Charles R Greathouse IV, <a href="/A185729/b185729.txt">Table of n, a(n) for n = 1..10000</a>

%e 51 is in the sequence because 51 = 2 + 4 + 5 + 6 + 7 + 8 + 9 + 10

%e (the sum of its first 8 non-divisors)

%t Select[Range[2600],MemberQ[Accumulate[Complement[Range[#],Divisors[#]]],#]&] (* _Harvey P. Dale_, Feb 16 2011 *)

%o (PARI) is(n)=my(s,t=1); while(s<n, if(n%t++, s+=t)); s==n \\ _Charles R Greathouse IV_, Nov 23 2015

%Y Cf. A185811 (k-values associated with this sequence)

%Y Cf. A064510.

%K nonn

%O 1,1

%A _Andrew Weimholt_, Feb 05 2011