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 A251605 #24 Feb 16 2021 02:51:26 %S A251605 226,1046,3881,20206,1970256,57619059,62109258 %N A251605 Numbers k = concat(s,t) such that k = antisigma(s) + antisigma(t), where antisigma(x) = A024816(x). %e A251605 226 = concat(22,6); 22*23/2 - sigma(22) = 253 - 36 = 217; 6*7/2 - sigma(6) = 21 - 12 = 9. Finally 217 + 9 = 226. %p A251605 with(numtheory): P:=proc(q) local s, t, k; global n; for n from 1 to q do for k from 1 to ilog10(n) do s:=n mod 10^k; t:=trunc(n/10^k); if s>0 then if s*(s+1)/2-sigma(s)+t*(t+1)/2-sigma(t)=n %p A251605 then print(n); break; fi; fi; od; od; end: P(10^7); %Y A251605 Cf. A000203, A024816, A253824, A253825. %K A251605 nonn,base,more %O A251605 1,1 %A A251605 _Paolo P. Lava_, Feb 02 2015 %E A251605 Incorrect term 240 removed by and a(6)-a(7) from _Jinyuan Wang_, Feb 16 2021