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A274028 Numbers whose sum of divisors and sum of anti-divisors are both palindromes. 1
1, 2, 3, 4, 5, 208, 211, 489, 39765, 41689, 43545, 45772, 1226372, 2028209, 3131006, 5639781, 45224913, 402664481, 509561899, 534611505 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

a(21) > 10^10. - Giovanni Resta, Jun 19 2016

LINKS

Table of n, a(n) for n=1..20.

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 A010347

Adjacent sequences:  A274025 A274026 A274027 * A274029 A274030 A274031

KEYWORD

nonn,base,more

AUTHOR

Paolo P. Lava, Jun 07 2016

EXTENSIONS

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

STATUS

approved

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Last modified June 22 02:16 EDT 2021. Contains 345367 sequences. (Running on oeis4.)