Search: id:A068310
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%I A068310
%S A068310 3,2,15,6,35,3,7,5,11,30,143,42,195,14,255,2,323,10,399,110,483,33,23,
%T A068310 39,3,182,87,210,899,15,1023,17,1155,34,1295,38,1443,95,1599,105,1763,
%U A068310 462,215,506,235,138,47,6,51,26,2703,78,2915,21,3135,203,3363,870,3599
%N A068310 n^2 - 1 divided by its largest square divisor.
%C A068310 In other words, squarefree part of n^2-1.
%C A068310 Least m for which x^2 - m*y^2 = 1 has a solution with x = n.
%e A068310 a(6) = 35, as 6^2 - 1 = 35 itself is squarefree.
%e A068310 7^2-1 = 48, whose largest square divisor is 16, so a(7) = 48/16=3.
%t A068310 a[n_] := Times@@(#[[1]] ^ Mod[ #[[2]], 2]&/@FactorInteger[n^2-1])
%o A068310 (PARI) a(n) = core(n*n - 1). - David Wasserman (wasserma(AT)spawar.navy.mil), 
               Mar 07 2005
%Y A068310 a(n) = A007913(n^2-1).
%Y A068310 Cf. A002350, A067872, A033314.
%Y A068310 Sequence in context: A145747 A055234 A086485 this_sequence A033314 A070260 
               A142705
%Y A068310 Adjacent sequences: A068307 A068308 A068309 this_sequence A068311 A068312 
               A068313
%K A068310 easy,nice,nonn
%O A068310 2,1
%A A068310 Lekraj Beedassy (blekraj(AT)yahoo.com), Feb 25 2002
%E A068310 Edited by Dean Hickerson (dean.hickerson(AT)yahoo.com), Mar 19 2002
%E A068310 Entry revised by N. J. A. Sloane (njas(AT)research.att.com), Apr 27 2007

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