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Smallest number that can be written in n ways as an unordered sum of 3 nonzero triangular numbers.
2

%I #5 Oct 19 2017 03:13:55

%S 0,3,12,30,61,52,82,136,142,147,192,277,247,367,552,457,516,507,646,

%T 637,721,822,787,1171,1066,1137,1227,1402,1192,1396,1696,1501,1612,

%U 1876,1927,1792,2551,2587,2926,2761,2422,2947,2887,3262,3271,3412,3937

%N Smallest number that can be written in n ways as an unordered sum of 3 nonzero triangular numbers.

%H Donovan Johnson, <a href="/A064181/b064181.txt">Table of n, a(n) for n = 0..3082</a>

%t a = Table[ n(n + 1)/2, {n, 1, 100} ]; b = {0}; c = Table[ 0, {5000} ]; Do[ b = Append[ b, a[ [ i ] ] + a[ [ j ] ] + a[ [ k ] ] ], {k, 1, 100}, {j, 1, k}, {i, 1, j} ]; b = Delete[ b, 1 ]; b = Sort[ b ]; l = Length[ b ]; Do[ If[ b[ [ n ] ] < 5000, c[ [ b[ [ n ] ] + 1 ] ]++ ], {n, 1, l} ]; Do[ k = 1; While[ c[ [ k ] ] != n, k++ ]; Print[ k - 1 ], {n, 0, 54} ]

%Y Cf. A063993.

%K nonn

%O 0,2

%A _Robert G. Wilson v_, Sep 20 2001

%E More terms from _Don Reble_, Sep 21 2001