A051611 - OEIS

%I #14 Jun 01 2016 11:37:06

%S 1,3,5,8,10,14,15,17,19,23,26,28,32,33,35,40,41,44,45,47,50,52,53,54,

%T 59,62,63,68,71,74,75,77,78,80,82,85,86,89,95,96,98,103,104,105,107,

%U 109,113,116,117,118,122,124,125,128,129,131,134,138,140,143,145,147

%N Numbers that are not the sum of 2 nonzero triangular numbers.

%C A053603(a(n)) = 0. - _Reinhard Zumkeller_, Jun 28 2013

%H T. D. Noe, <a href="/A051611/b051611.txt">Table of n, a(n) for n=1..1000</a>

%t notSumQ[n_] := Reduce[ 0 < x <= y && n == x*(x + 1)/2 + y*(y + 1)/2, {x, y}, Integers] === False; Select[ Range[150], notSumQ] (* _Jean-François Alcover_, Jun 27 2012 *)

%t With[{trnos=Accumulate[Range[100]]},Complement[Range[150],Total/@ Tuples[ trnos,2]]] (* _Harvey P. Dale_, Jun 01 2016 *)

%o (Haskell)

%o a051611 n = a051611_list !! (n-1)

%o a051611_list = filter ((== 0) . a053603) [1..]

%o -- _Reinhard Zumkeller_, Jun 28 2013

%Y Integers not in the sequence A051533. Cf. A002097, A000217, A007294, A051611, A053603.

%K easy,nonn,nice

%O 1,2

%A Klaus Strassburger (strass(AT)ddfi.uni-duesseldorf.de)