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A212794
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Triangular numbers (A000217) which are also hypotenuse numbers (A009003).
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1
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10, 15, 45, 55, 78, 91, 105, 120, 136, 153, 190, 210, 300, 325, 351, 406, 435, 465, 561, 595, 630, 666, 703, 741, 780, 820, 861, 990, 1035, 1225, 1275, 1326, 1378, 1431, 1485, 1540, 1653, 1711, 1770, 1830, 1891, 2080, 2145, 2278, 2346, 2415, 2485, 2628
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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LINKS
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MAPLE
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ishyp:= proc(n) ormap(t -> t mod 4 = 1, numtheory:-factorset(n)) end proc:
select(ishyp, [seq(i*(i+1)/2, i=1..100)]); # Robert Israel, Jun 02 2023
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MATHEMATICA
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A212794list[upto_]:=Select[PolygonalNumber[Range[4, upto]], AnyTrue[Map[Mod[First[#], 4]==1&, FactorInteger[#]], TrueQ]&]; A212794list[100] (* Paolo Xausa, Jul 28 2023 *)
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PROG
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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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