%I #7 Apr 10 2021 20:20:52
%S 1,3,6,10,20,43,64,114,185,280,402,554,820,11030,14640,18910,24177,
%T 30439,37810,88410,107416,129286,154290,270000,317530,371359,431306,
%U 659350,758210,867695,988534,1394984,1576972,1775485,2383290,2665338,3459466,3846532
%N a(n) = t(n)_t(n) where t() = triangular numbers A000217.
%C See A122618 for notation.
%H Alois P. Heinz, <a href="/A122628/b122628.txt">Table of n, a(n) for n = 1..10000</a>
%p a:= n-> (b-> (l-> add(l[i]*b^(i-1),
%p i=1..nops(l)))(convert(b, base, 10)))(n*(n+1)/2):
%p seq(a(n), n=1..35); # _Alois P. Heinz_, Apr 10 2021
%K nonn,base
%O 1,2
%A _N. J. A. Sloane_, Sep 21 2006