Search: id:A074377
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%I A074377
%S A074377 0,1,7,10,22,27,45,52,76,85,115,126,162,175,217,232,280,297,351,370,
%T A074377 430,451,517,540,612,637,715,742,826,855,945,976,1072,1105,1207,1242,
%U A074377 1350,1387,1501,1540,1660,1701,1827,1870,2002,2047,2185,2232,2376,2425
%N A074377 Odd triangular numbers decremented and halved.
%C A074377 Also called generalized 10-gonal numbers. - T. D. Noe (noe(AT)sspectra.com), 
               Apr 21 2006
%H A074377 Neville Holmes, <a href="http://www.comp.utas.edu.au/users/nholmes/sqncs/
               gmtrc.htm#A074377">More Gemometric Integer Sequences</a>
%F A074377 (n(n+1)-2)/4 where n(n+1)/2 is odd.
%F A074377 G.f.: x(1+6x+x^2)/((1-x)(1-x^2)^2). - Michael Somos, Mar 04 2003
%F A074377 a(2k) = k(4k+3); a(2k+1) = (2k+1)^2+k. [From Benoit Jubin (benoit_jubin(AT)yahoo.fr), 
               Feb 05 2009]
%o A074377 (PARI) a(n)=(2*n+3-4*(n%2))*(n-n\2)
%Y A074377 Cf. A011848, A014493, A074378.
%Y A074377 Cf. A001107 (10-gonal numbers).
%Y A074377 Sequence in context: A064210 A097634 A120312 this_sequence A117618 A103119 
               A054224
%Y A074377 Adjacent sequences: A074374 A074375 A074376 this_sequence A074378 A074379 
               A074380
%K A074377 easy,nonn
%O A074377 0,3
%A A074377 Neville Holmes (neville.holmes(AT)utas.edu.au), Sep 04 2002

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