%I A076921
%S A076921 1,1,2,4,6,9,12,16,20,25,30,36,42,49,56,64,72,81,90,100,110,121,132,
%T A076921 144,156,169,182,196,210,225,240,256,272,289,306,324,342,361,380,400,
%U A076921 420,441,462,484,506,529,552,576,600,625,650,676,702,729,756,784
%N A076921 Smallest number such that the highest common factor of pair of successive 
               terms follows the pattern 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 
               7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, ... i.e. b(2n-1)=b(2n)= 
               n given by A004526.
%C A076921 (1) a(2n) = n^2, a(2n-1) = n(n+1) = twice the n-th triangular number. 
               (2) Geometric mean of the successive squares interleaved between 
               them.
%C A076921 Essentially the same as A002620.
%Y A076921 Cf. A004526.
%Y A076921 Sequence in context: A086378 A088900 A083392 this_sequence A002620 A087811 
               A025699
%Y A076921 Adjacent sequences: A076918 A076919 A076920 this_sequence A076922 A076923 
               A076924
%K A076921 nonn
%O A076921 1,3
%A A076921 Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Oct 17 2002
%E A076921 More terms from Philippe DELEHAM, Jun 20 2005