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A300447 Numbers x such that sigma(x) = sigma(y), with x<>y, where y is the 10's complement mod 10 of the digits of x. 2
54, 56, 513, 520, 546, 564, 580, 597, 4845, 5130, 5223, 5454, 5656, 5887, 5970, 6265, 44226, 46365, 48450, 50260, 50840, 51300, 52230, 52520, 53768, 57342, 58580, 58870, 59700, 62650, 64745, 66884, 463650, 477972, 484500, 489132, 489632, 493752, 501536, 503274 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..150

EXAMPLE

sigma(54) = sigma(56) = 120;

sigma(513) = sigma(597) = 800;

sigma(477972) = sigma(633138) = 1415232.

MAPLE

with(numtheory): P:=proc(q) local a, b, k, n;

for n from 1 to q do a:=convert(n, base, 10);

for k from 1 to nops(a) do a[k]:=(10-a[k]) mod 10; od; b:=0;

for k from 1 to nops(a) do b:=b*10+a[nops(a)-k+1]; od;

if b<>n and sigma(b)=sigma(n) then print(n); fi; od; end: P(10^6);

MATHEMATICA

Select[Range[10^6], Apply[And[#1 != #2, DivisorSigma[1, #1] == DivisorSigma[1, #2]] &, {#, FromDigits[IntegerDigits[#] /. d_?Positive :> 10 - d]}] &] (* Michael De Vlieger, Mar 09 2018 *)

PROG

(PARI) isok(x) = {my(dx = digits(x), dy = vector(#dx, k, (10-dx[k]) % 10), y = fromdigits(dy)); (x != y) && (sigma(x) == sigma(y)); } \\ Michel Marcus, Mar 07 2018

CROSSREFS

Cf. A000203, A055120.

Sequence in context: A107936 A252722 A326181 * A295696 A095561 A095551

Adjacent sequences:  A300444 A300445 A300446 * A300448 A300449 A300450

KEYWORD

nonn,base,easy

AUTHOR

Paolo P. Lava, Mar 06 2018

STATUS

approved

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Last modified April 17 11:50 EDT 2021. Contains 343064 sequences. (Running on oeis4.)