This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A256087 #9 Nov 04 2024 18:17:02 %S A256087 364,420,476,492,532,548,604,640,660,708,728,764,820,836,876,892,948, %T A256087 984,1004,1052,1072,1108,1164,1180,1220,1236,1292,1328,1348,1396,1416, %U A256087 1452,1508,1524,1564,1580,1636,1672,1692,1740,1760,1796,1852,1868,1908,1924,1980 %N A256087 Non-palindromic balanced numbers in base 7. %C A256087 Here a number is called balanced if the sum of digits weighted by their arithmetic distance from the "center" is zero. Since palindromes (A029954) are trivially balanced, they are excluded here. %C A256087 This is the base-7 variant of the decimal version A256075 invented by Eric Angelini. See there, and the base-2 version A256082, for further information and examples. %H A256087 Robert Israel, <a href="/A256087/b256087.txt">Table of n, a(n) for n = 1..10000</a> %p A256087 filter:= proc(n) local L, m,i; %p A256087 L:= convert(n, base, 7); %p A256087 m:= (1+nops(L))/2; %p A256087 add(L[i]*(i-m), i=1..nops(L))=0 and L <> ListTools:-Reverse(L) %p A256087 end proc: %p A256087 select(filter, [$1..10000]); # _Robert Israel_, Nov 04 2024 %o A256087 (PARI) is(n,b=7,d=digits(n,b),o=(#d+1)/2)=!(vector(#d,i,i-o)*d~)&&d!=Vecrev(d) %Y A256087 Cf. A256082 - A256089, A256075, A256080, A029954. %K A256087 nonn,base %O A256087 1,1 %A A256087 _M. F. Hasler_, Mar 14 2015