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%I #5 Aug 21 2016 14:34:30
%S 3,7,7,12,13,13,19,19,21,21,27,28,28,31,31,37,37,39,39,43,43,48,49,49,
%T 52,52,57,57,61,61,63,63,67,67,73,73,75,76,76,79,79,84,84,91,91,91,91,
%U 93,93,97,97,103,103,108,109,109,111,111,112,112,117,117,124,124,127,127,129,129,133
%N a(n) = number in position n when all i^2 - i*j + j^2, where 1 <= i < j are arranged in increasing order.
%p A024612 := proc(n)
%p local i,j,disc;
%p # n=i^2+j^2-i*j = (j-i)^2+i*j, 1<=i<j
%p # so (j-i)>=1 and i*j>=j and i^2+j^2-i*j >= 1+j max search radius
%p for j from 2 to n-1 do
%p # i=(j +- sqrt(4n-3j^2))/2
%p disc := 4*n-3*j^2 ;
%p if disc >= 0 then
%p if issqr(disc) then
%p i := (j+sqrt(disc))/2 ;
%p if type(i,'integer') and i >= 1 and i<j then
%p printf("%d,",n) ;
%p end if;
%p if disc > 0 then
%p i := (j-sqrt(disc))/2 ;
%p if type(i,'integer') and i >= 1 and i<j then
%p printf("%d,",n) ;
%p end if;
%p end if;
%p end if;
%p end if;
%p end do:
%p end proc:
%p for t from 1 to 120 do
%p A024612(t);
%p end do: # _R. J. Mathar_, Aug 21 2016
%K nonn
%O 1,1
%A _Clark Kimberling_
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