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A274049 Numbers k such that sum of anti-divisors of k is palindromic.

%I A274049 #21 Jun 18 2025 11:33:10
%S A274049 1,2,3,4,5,6,8,9,21,40,42,53,76,84,127,137,143,150,163,173,177,199,
%T A274049 208,211,229,236,242,249,252,255,273,277,288,289,298,316,320,321,323,
%U A274049 329,332,334,335,336,351,372,401,411,419,431,434,437,467,475,477,485,489,497
%N A274049 Numbers k such that sum of anti-divisors of k is palindromic.
%C A274049 A274028 is a subset of this sequence.
%H A274049 Paolo P. Lava, <a href="/A274049/b274049.txt">Table of n, a(n) for n = 1..1300</a>
%e A274049 Anti-divisors of 150 are 4, 7, 12, 13, 20, 23, 43, 60, 100 and their sum is 282 that is palindromic.
%p A274049 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 A274049 P:=proc(q) local a,j,k,n; for n from 1 to q do k:=0; j:=n; while j mod 2 <> 1 do
%p A274049 k:=k+1; j:=j/2; od; a:=sigma(2*n+1)+sigma(2*n-1)+sigma(n/2^k)*2^(k+1)-6*n-2;
%p A274049 if T(a)=a then print(n); fi; od; end: P(10^12);
%Y A274049 Cf. A066417, A073956, A274028.
%K A274049 nonn,base
%O A274049 1,2
%A A274049 _Paolo P. Lava_, Jun 08 2016