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

1, 2, 3, 4, 5, 208, 211, 489, 39765, 41689, 43545, 45772, 1226372, 2028209, 3131006, 5639781, 45224913, 402664481, 509561899, 534611505, 30392347941, 37824872279, 42100531202, 67332408085, 208185050013, 363340615629, 1316050604902, 1792459658755, 2465601425469

Offset

1,2

Comments

Intersection of A028980 and A274049. - Michel Marcus, Jun 08 2016

Links

Table of n, a(n) for n=1..29.

Example

Anti-divisors of 208 are 3, 5, 32, 83, 139 and their sum is 262 ; sigma(208) = 434.

Maple

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:=proc(q) local a, j, k, n, t; print(1); for n from 1 to q do k:=0; j:=n;
while j mod 2 <> 1 do 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;
if T(a)=a and sigma(n)=T(sigma(n)) then print(n); fi; od; end: P(10^6);

Crossrefs

Cf. A000203, A002113, A028980, A066417, A073956, A274049.

Sequence in context: A318842 A298671 A073787 * A037436 A115900 A349486

Adjacent sequences: A274025 A274026 A274027 * A274029 A274030 A274031

Keyword

nonn,base

Author

Paolo P. Lava, Jun 07 2016

Extensions

Missing a(1)-a(2) and a(17)-a(20) from Giovanni Resta, Jun 19 2016

a(21)-a(29) from Max Alekseyev, Jan 28 2024

Status

approved