cp's OEIS Frontend

A282108 Numbers n with k digits in base x (MSD(n)=d_k, LSD(n)=d_1) such that, chosen one of their digits in position d_k < j < d_1, is Sum_{i=j+1..k}{(i-j)*d_i} = Sum_{i=1..j-1}{(j-i)*d_i}. Case x = 3.

%I A282108 #11 May 30 2019 08:58:47
%S A282108 10,13,16,20,23,26,29,30,32,35,39,48,55,60,64,69,73,78,82,87,90,91,96,
%T A282108 100,105,112,117,121,130,137,142,144,146,151,155,160,164,165,169,173,
%U A282108 178,180,182,187,192,194,203,207,212,219,224,233,234,242,246,247,256
%N A282108 Numbers n with k digits in base x (MSD(n)=d_k, LSD(n)=d_1) such that, chosen one of their digits in position d_k < j < d_1, is Sum_{i=j+1..k}{(i-j)*d_i} = Sum_{i=1..j-1}{(j-i)*d_i}. Case x = 3.
%C A282108 All the palindromic numbers in base 3 with an odd number of digits belong to the sequence.
%C A282108 Here the fulcrum is one of the digits while in the sequence from A282143 to A282151 is between two digits.
%H A282108 Paolo P. Lava, <a href="/A282108/b282108.txt">Table of n, a(n) for n = 1..10000</a>
%e A282108 35 in base 3 is 1022. If j = 2 (second 2 from the right) we have 0*1 + 1*2 = 2 for the left side and 2*1 for the right one.
%p A282108 P:=proc(n,h) local a,j,k: a:=convert(n, base, h):
%p A282108 for k from 1 to nops(a)-1 do
%p A282108 if add(a[j]*(k-j),j=1..k)=add(a[j]*(j-k),j=k+1..nops(a))
%p A282108 then RETURN(n); break: fi: od: end: seq(P(i,3),i=1..10^3);
%Y A282108 Cf. A282107, A282109 - A282115.
%K A282108 base,nonn,easy
%O A282108 1,1
%A A282108 _Paolo P. Lava_, Feb 06 2017