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A246753
Triangular numbers with strictly increasing product of digits.
3
1, 3, 6, 28, 36, 45, 55, 66, 78, 276, 378, 496, 595, 1596, 2485, 2775, 3486, 4656, 5565, 5778, 5995, 8778, 25878, 26796, 35778, 47586, 47895, 58996, 196878, 277885, 359976, 378885, 448878, 468996, 569778, 786885, 887778, 2489796, 2797795, 3667986, 3689686, 3887866
OFFSET
1,2
LINKS
EXAMPLE
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.
MATHEMATICA
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
DeleteDuplicates[{#, Times@@IntegerDigits[#]}&/@Accumulate[Range[3000]], GreaterEqual[#1[[2]], #2[[2]]]&][[;; , 1]] (* Harvey P. Dale, Oct 29 2024 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, Sep 02 2014
STATUS
approved