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A257019
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Numbers whose quarter-square representation consists of two terms.
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10
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3, 5, 7, 8, 10, 11, 13, 14, 17, 18, 21, 22, 24, 26, 27, 29, 31, 32, 34, 37, 38, 40, 43, 44, 46, 48, 50, 51, 53, 55, 57, 58, 60, 62, 65, 66, 68, 70, 73, 74, 76, 78, 82, 83, 85, 87, 91, 92, 94, 96, 99, 101, 102, 104, 106, 109, 111, 112, 114, 116, 119, 122, 123
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OFFSET
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1,1
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COMMENTS
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Every positive integer is a sum of at most four distinct quarter squares (see A257019).
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LINKS
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EXAMPLE
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Quarter-square representations:
r(0) = 0, one term
r(1) = 1, one term
r(3) = 2 + 1, two terms, so a(1) = 3
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MATHEMATICA
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z = 100; b[n_] := Floor[(n + 1)^2/4]; bb = Table[b[n], {n, 0, 100}];
s[n_] := Table[b[n], {k, b[n + 1] - b[n]}];
h[1] = {1}; h[n_] := Join[h[n - 1], s[n]];
g = h[100]; r[0] = {0};
r[n_] := If[MemberQ[bb, n], {n}, Join[{g[[n]]}, r[n - g[[n]]]]];
u = Table[Length[r[n]], {n, 0, 4 z}]; (* A257023 *)
Flatten[-1 + Position[u, 1]]; (* A002620 *)
Flatten[-1 + Position[u, 2]]; (* A257019 *)
Flatten[-1 + Position[u, 3]]; (* A257020 *)
Flatten[-1 + Position[u, 4]]; (* A257021 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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