A072566 - OEIS

A072566

Numbers n such that n and sigma(n) end with the same digit in base 10.

1, 14, 34, 40, 44, 74, 78, 81, 84, 94, 120, 124, 134, 138, 164, 190, 194, 198, 204, 214, 224, 244, 254, 258, 270, 274, 280, 284, 290, 294, 314, 318, 334, 360, 361, 364, 380, 394, 404, 438, 440, 441, 444, 454, 462, 498, 514, 520, 524, 528, 540, 544, 554, 558

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

Probably lim n -> infinity a(n)/n = 10.

MAPLE

filter:= n -> numtheory:-sigma(n)-n mod 10 = 0:

select(filter, [$1..1000]); # Robert Israel, Feb 28 2020

MATHEMATICA

Select[Range[600], Mod[#, 10]==Mod[DivisorSigma[1, #], 10]&] (* Harvey P. Dale, Mar 07 2024 *)