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A072524
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Sum of the remainders when the n-th triangular number is divided by all smaller triangular numbers > 1.
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2
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0, 0, 0, 5, 8, 10, 33, 35, 37, 86, 87, 122, 112, 207, 215, 255, 354, 389, 448, 493, 633, 710, 681, 1016, 1042, 1214, 1420, 1518, 1645, 1654, 2050, 2180, 2276, 2828, 2654, 3124, 3131, 3751, 3770, 4267, 4465, 4971, 5170, 5759, 6282, 6315, 6807, 7587, 7419
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OFFSET
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1,4
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LINKS
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EXAMPLE
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The eighth triangular number is 36; division by 3, 6, 10, 15,21, 28 gives the remainders 0, 0, 6, 6, 15, 8, so a(8) = 0 + 0 + 6+ 6 + 15 + 8 = 35.
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MATHEMATICA
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sr[x_]:=Total[Mod[Last[x], x[[2;; Length[x]-1]]]]; Module[{nn=50, tr}, tr= Accumulate[ Range[nn]]; Join[{0}, Table[sr[Take[tr, n]], {n, 2, nn}]]] (* Harvey P. Dale, Oct 14 2017 *)
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PROG
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(PARI) for(n=1, 50, s=0; for(j=2, n-1, s=s+binomial(n+1, 2)%binomial(j+1, 2)); print1(s, ", "))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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