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A234004
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Smallest number which is the sum of two positive triangular numbers (A000217) in at least n ways.
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1
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2, 16, 81, 471, 1056, 1381, 6906, 6906, 17956, 34531, 40056, 40056, 200281, 200281, 200281, 200281, 520731, 520731, 1001406, 1001406, 1482081, 1482081, 1482081, 1482081, 7410406, 7410406, 7410406, 7410406, 7410406, 7410406, 7410406, 7410406
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OFFSET
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1,1
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LINKS
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EXAMPLE
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2 = 1+1; 16 = 1+15 = 6+10; 81 = 3+78 = 15+66 = 36+45.
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MATHEMATICA
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poly[n_, k_]:=n (n-1)(k-2)/2+n; nn=10^5; order=3; t2=Table[0, {nn}]; n2=Floor[(-4+#+Sqrt[(-4+#)^2+8 (-2+#) nn])/(2 (-2+#))&[order]]; Do[r=Plus@@poly[{a, b}, order]; If[r<=nn, t2[[r]]++], {a, n2}, {b, a, n2}]; t={}; n=1; While[a=Position[t2, _?(#>=n&), 1, 1]; a!={}, AppendTo[t, a[[1, 1]]]; n++]; t (* after T. D. Noe (A048610) *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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