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 A295769 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. 3
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Duplicates in the products are allowed. A subsequence of A188630. LINKS EXAMPLE 630 = 105*6 = 21*10*3. 990 = 66*15 = 55*6*3. MAPLE 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: A295769(200000); # Peter Luschny, Dec 21 2017 CROSSREFS Cf. A000217, A188630. Sequence in context: A177421 A333503 A173423 * A110904 A171258 A234245 Adjacent sequences:  A295766 A295767 A295768 * A295770 A295771 A295772 KEYWORD nonn AUTHOR Alex Ratushnyak, Nov 27 2017 STATUS approved

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Last modified June 1 04:37 EDT 2020. Contains 334758 sequences. (Running on oeis4.)