Search: id:A016970
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%I A016970
%S A016970 25,121,289,529,841,1225,1681,2209,2809,3481,4225,5041,
%T A016970 5929,6889,7921,9025,10201,11449,12769,14161,15625,17161,
%U A016970 18769,20449,22201,24025,25921,27889,29929,32041,34225
%N A016970 (6n+5)^2.
%C A016970 The product of 4 successive terms of an arithmetic progression + square 
               of the common difference is a square: a(n) = the square arising as 
               the sum of first four terms of an arithmetic progression + n^2 where 
               1 is the first term and n is the common difference. a(1) = 25 = 1*2*3*4+1 
               a(2) = 121 = 1*3*5*7 +2^2 a(3) = 289 = 1*4*7*10 + 3^2, etc. - Amarnath 
               Murthy (amarnath_murthy(AT)yahoo.com), Mar 25 2004
%C A016970 If Y is a fixed 2-subset of a (6n+1)-set X then a(n-1) is the number 
               of 3-subsets of X intersecting Y. - Milan R. Janjic (agnus(AT)blic.net), 
               Oct 21 2007
%H A016970 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Two Enumerative 
               Functions</a>
%Y A016970 Sequence in context: A036057 A083509 A031151 this_sequence A062938 A141722 
               A090159
%Y A016970 Adjacent sequences: A016967 A016968 A016969 this_sequence A016971 A016972 
               A016973
%K A016970 nonn,easy
%O A016970 0,1
%A A016970 N. J. A. Sloane (njas(AT)research.att.com).

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