Search: id:A116541
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%I A116541
%S A116541 1,28,45,153,171,325,496,2016,3321,4753,4950,7260,7381,8256,11628,13203,
%T A116541 14196,20100,29161,41616,56953,64620,65341,73536,76636,77028,89676,
%U A116541 90100,97461,101475,126756,130816,150975,166176,166753,179700,180300
%N A116541 Triangular numbers for which the number of divisors is also a triangular 
               number.
%e A116541 496 is in the sequence because it is a triangular number (31*32/2) and 
               has 10=4*5/2 divisors (1,2,4,8,16,31,62,124,248,496).
%p A116541 with(numtheory): a:=proc(n) local s: s:=tau(n*(n+1)/2): if type(sqrt(1+8*s)/
               2-1/2,integer)=true then n*(n+1)/2 else fi end: seq(a(n),n=1..750); 
               - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 06 2006
%t A116541 Select[ Range(AT)600/2*(Range(AT)600 + 1), IntegerQ(AT) Sqrt[8DivisorSigma[0, 
               # ] + 1] &] (from Robert G. Wilson v (rgwv(at)rgwv.com), Apr 20 2006).
%Y A116541 Sequence in context: A061826 A144581 A075875 this_sequence A116565 A156719 
               A039615
%Y A116541 Adjacent sequences: A116538 A116539 A116540 this_sequence A116542 A116543 
               A116544
%K A116541 nonn
%O A116541 1,2
%A A116541 Luc Stevens (lms022(AT)yahoo.com), Apr 03 2006
%E A116541 More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 06 2006

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