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%I #10 Oct 29 2024 15:09:16
%S 1,3,6,28,36,45,55,66,78,276,378,496,595,1596,2485,2775,3486,4656,
%T 5565,5778,5995,8778,25878,26796,35778,47586,47895,58996,196878,
%U 277885,359976,378885,448878,468996,569778,786885,887778,2489796,2797795,3667986,3689686,3887866
%N Triangular numbers with strictly increasing product of digits.
%H K. D. Bajpai, <a href="/A246753/b246753.txt">Table of n, a(n) for n = 1..159</a>
%e a(4) = 28 = 7 * (7 + 1) / 2, which is 7th triangular number with product of digits = 2 * 8 = 16. a(5) = 36 = 8 * (8 + 1) / 2, which is 8th triangular number with product of digits = 3 *6 = 18. Since 18 > 16, 28 and 36 are in list.
%t A246753 = {}; t = 0; Do[k = n*(n + 1)/2; s = Apply[Times, IntegerDigits[k]];If[s > t, t = s; AppendTo[A246753, k]], {n, 1, 100}]; A246753
%t DeleteDuplicates[{#,Times@@IntegerDigits[#]}&/@Accumulate[Range[3000]],GreaterEqual[#1[[2]],#2[[2]]]&][[;;,1]] (* _Harvey P. Dale_, Oct 29 2024 *)
%Y Cf. A000217, A007954, A230041.
%K nonn,base
%O 1,2
%A _K. D. Bajpai_, Sep 02 2014