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 A130121 a(1)=1. a(n) = number of earlier terms of the sequence which divide n(n+1)/2. 2

%I

%S 1,1,2,3,3,4,4,7,4,2,6,7,4,6,12,8,4,4,4,10,6,2,18,19,2,4,14,9,4,4,17,

%T 23,5,6,19,14,4,6,27,19,6,6,6,20,7,3,30,35,7,7,18,6,7,8,29,41,9,3,22,

%U 22,2,14,47,23,7,6,8,24,17,11,37,37,4,9,27,23,14,6,25,50,12,3,34,41,5,8,41

%N a(1)=1. a(n) = number of earlier terms of the sequence which divide n(n+1)/2.

%H Robert Israel, <a href="/A130121/b130121.txt">Table of n, a(n) for n = 1..10000</a>

%p a[1]:=1: for n from 2 to 110 do a[n]:=0: for j from 1 to n-1 do if type(n*(n+1)/2/a[j], integer)=true then a[n]:=a[n]+1 else fi: od: od: seq(a[n],n=1..110); # _Emeric Deutsch_, May 19 2007

%Y Cf. A130120.

%K nonn

%O 1,3

%A _Leroy Quet_, May 10 2007

%E More terms from _Emeric Deutsch_, May 19 2007

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Last modified February 4 02:26 EST 2023. Contains 360045 sequences. (Running on oeis4.)