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A295769
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Triangular numbers that can be represented as a product of two triangular numbers greater than 1, and as a product of three triangular numbers greater than 1.
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3
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630, 990, 4095, 15400, 19110, 25200, 37128, 61425, 79800, 105570, 122265, 145530, 176715, 192510, 437580, 500500, 749700, 828828, 1185030, 2031120, 2162160, 2821500, 4279275, 4573800, 4744740, 4959675, 5364450, 6053460, 7556328, 8817900, 13857480, 15992340
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OFFSET
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1,1
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COMMENTS
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Duplicates in the products are allowed.
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LINKS
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EXAMPLE
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630 = 105*6 = 21*10*3.
990 = 66*15 = 55*6*3.
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MAPLE
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A295769 := proc(limit) local t, E, G, n, k, j, c, b, d, ist; E:=NULL; G:=NULL;
t := proc(n) option remember; iquo(n*(n+1), 2) end;
ist := proc(n) option remember; n = t(floor(sqrt(2*n))) end;
for n from 2 do
c := t(n); if c > limit then break fi;
for k from 2 do
b := c*t(k); if b > limit then break fi;
if ist(b) then E := E, b fi;
for j from 2 do
d := b*t(j); if d > limit then break fi;
if ist(d) then G := G, d fi
od od od; {E} intersect {G} end:
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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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