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 A212616 Least triangular number that is the product of n triangular numbers greater than 1. 7
 3, 36, 300, 1485, 3240, 265356, 265356, 21520080, 21520080, 193720086, 1743362676, 141214502520, 141214502520, 11438393835996, 11438393835996, 926510072902560, 926510072902560, 75047317454789316, 75047317454789316, 6078832727785072200, 6078832727785072200 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE Contribution from Donovan Johnson, Jun 11 2012: (Start) Let tri(n) = n*(n+1)/2. Then a(1)  = 3 = tri(2). a(2)  = 36 = tri(3)^2. a(3)  = 300 = tri(2) * tri(4)^2. a(4)  = 1485 = tri(2)^3 * tri(10). a(5)  = 3240 = tri(2)^2 * tri(3)^2 * tri(4). a(6)  = 265356 = tri(2)^4 * tri(8) * tri(13).         265356 = tri(2)^3 * tri(3) * tri(6) * tri(12). a(7)  = 265356 = tri(2)^4 * tri(3)^2 * tri(13). a(8)  = 21520080 = tri(2)^6 * tri(8) * tri(40). a(9)  = 21520080 = tri(2)^6 * tri(3)^2 * tri(40). a(10) = 193720086 = tri(2)^7 * tri(3) * tri(6) * tri(37). a(11) = 1743362676 = tri(2)^8  * tri(3)^2 * tri(121). a(12) = 141214502520 = tri(2)^10 * tri(8) * tri(364).         141214502520 = tri(2)^8 * tri(3) * tri(5) * tri(13) * tri(72). a(13) = 141214502520 = tri(2)^10 * tri(3)^2 * tri(364).         141214502520 = tri(2)^10 * tri(4) * tri(13) * tri(72). a(14) = 11438393835996 = tri(2)^12 * tri(8) * tri(1093). a(15) = 11438393835996 = tri(2)^12 * tri(3)^2 * tri(1093). a(16) = 926510072902560 = tri(2)^14 * tri(8) * tri(3280). a(17) = 926510072902560 = tri(2)^14 * tri(3)^2 * tri(3280). a(18) = 75047317454789316 = tri(2)^16 * tri(8) * tri(9841). a(19) = 75047317454789316 = tri(2)^16 * tri(3)^2 * tri(9841). a(20) = 6078832727785072200 = tri(2)^18 * tri(8) * tri(29524). a(21) = 6078832727785072200 = tri(2)^18 * tri(3)^2 * tri(29524). (End) CROSSREFS Cf. A000217 (triangular numbers). Cf. A212617, A225066-A225070 (5- to 10-gonal cases). Sequence in context: A005446 A056307 A056299 * A073980 A034860 A220831 Adjacent sequences:  A212613 A212614 A212615 * A212617 A212618 A212619 KEYWORD nonn AUTHOR T. D. Noe, Jun 11 2012 EXTENSIONS Terms a(3) to a(21) by Donovan Johnson, Jun 11 2012 STATUS approved

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Last modified October 14 07:30 EDT 2019. Contains 327995 sequences. (Running on oeis4.)