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A191856 First factor in happy factorization of n-th rhombic number.

%I A191856 #12 Feb 28 2020 22:11:24
%S A191856 1,7,2,1,3,1,23,4,1,31,16,5,2,1,47,6,1,1,7,1,71,25,79,8,1,3,4,13,48,9,
%T A191856 103,2,1,5,119,10,1,127,64,1,27,34,1,11,151,4,3,80,1,167,12,1,7,22,1,
%U A191856 1,191,96,13,199,2,8,1,43,4,73,223,14,1,3,2,5,239
%N A191856 First factor in happy factorization of n-th rhombic number.
%C A191856 a(n) = A007966(A007970(n)) = A007970(n) / A191857(n);
%C A191856 (a(n), A191857(n)) is a 2-happy couple;
%C A191856 notation: D in the Conway link.
%H A191856 Reinhard Zumkeller, <a href="/A191856/b191856.txt">Table of n, a(n) for n = 1..99</a>
%H A191856 J. H. Conway, <a href="http://www.cs.uwaterloo.ca/journals/JIS/happy.html">On Happy Factorizations</a>, J. Integer Sequences, Vol. 1, 1998, #1.
%o A191856 (Haskell)
%o A191856 a191856 = a007966 . a007970  -- _Reinhard Zumkeller_, Oct 11 2015
%Y A191856 Cf. A007966, A007970, A191857.
%K A191856 nonn
%O A191856 1,2
%A A191856 _Reinhard Zumkeller_, Jun 18 2011
%E A191856 Wrong formula removed (thanks to _Wolfdieter Lang_, who pointed this out) by _Reinhard Zumkeller_, Oct 11 2015