cp's OEIS Frontend

A274028 Numbers whose sum of divisors and sum of anti-divisors are both palindromes.

%I A274028 #19 Jan 31 2024 15:06:37
%S A274028 1,2,3,4,5,208,211,489,39765,41689,43545,45772,1226372,2028209,
%T A274028 3131006,5639781,45224913,402664481,509561899,534611505,30392347941,
%U A274028 37824872279,42100531202,67332408085,208185050013,363340615629,1316050604902,1792459658755,2465601425469
%N A274028 Numbers whose sum of divisors and sum of anti-divisors are both palindromes.
%C A274028 Intersection of A028980 and A274049. - _Michel Marcus_, Jun 08 2016
%e A274028 Anti-divisors of 208 are 3, 5, 32, 83, 139 and their sum is 262 ; sigma(208) = 434.
%p A274028 with(numtheory): T:=proc(w) local x, y, z; x:=w; y:=0;for z from 1 to ilog10(x)+1 do y:=10*y+(x mod 10); x:=trunc(x/10); od; y; end:
%p A274028 P:=proc(q) local a,j,k,n,t; print(1); for n from 1 to q do k:=0; j:=n;
%p A274028 while j mod 2 <> 1 do k:=k+1; j:=j/2; od;
%p A274028 a:=sigma(2*n+1)+sigma(2*n-1)+sigma(n/2^k)*2^(k+1)-6*n-2;
%p A274028 if T(a)=a and sigma(n)=T(sigma(n)) then print(n); fi; od; end: P(10^6);
%Y A274028 Cf. A000203, A002113, A028980, A066417, A073956, A274049.
%K A274028 nonn,base
%O A274028 1,2
%A A274028 _Paolo P. Lava_, Jun 07 2016
%E A274028 Missing a(1)-a(2) and a(17)-a(20) from _Giovanni Resta_, Jun 19 2016
%E A274028 a(21)-a(29) from _Max Alekseyev_, Jan 28 2024