Search: id:A031149
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%I A031149
%S A031149 4,7,13,16,19,38,57,136,253,487,604,721,1442,2163,5164,9607,18493,
%T A031149 22936,27379,54758,82137,196096,364813,702247,870964,1039681,
%U A031149 2079362,3119043,7446484,13853287,26666893,33073696,39480499
%N A031149 Numbers n such that n^2 with last digit deleted is still a perfect square.
%C A031149 Square root of 'Squares from A023110'.
%F A031149 Appears to satisfy: a(n)=38a(n-7)-a(n-14) which would require a(-k) to 
               look like 3, 2, 1, 4, 7, 13, 16, 57, 38, 19, 136, ... for k>0. - 
               Henry Bottomley (se16(AT)btinternet.com), May 08 2001
%e A031149 364813^2 = 133088524969, 115364^2 = 13308852496
%p A031149 for i from 1 to 150000 do if (floor(sqrt(10 * i^2 + 9)) > floor(sqrt(10 
               * i^2))) then print(floor(sqrt(10 * i^2 + 9))) end if end do;
%Y A031149 Cf. A023110, A030686, A030687, A031150.
%Y A031149 Sequence in context: A084089 A137827 A045090 this_sequence A074273 A125758 
               A151788
%Y A031149 Adjacent sequences: A031146 A031147 A031148 this_sequence A031150 A031151 
               A031152
%K A031149 nonn,base
%O A031149 1,1
%A A031149 Patrick De Geest (pdg(AT)worldofnumbers.com)

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