OFFSET
1,2
LINKS
K. D. Bajpai, Table of n, a(n) for n = 1..159
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