A057529 -id:A057529 - cp's OEIS frontend

A057530 n is odd and divisible by number of divisors of n and sum of digits of n.

1, 9, 225, 441, 1521, 2025, 2601, 12321, 40401, 62001, 99225, 103041, 251001, 321489, 585225, 893025, 1022121, 1108809, 1212201, 1320201, 1946025, 2368521, 2480625, 2772225, 3101121, 3744225, 4473225, 4862025, 5517801, 6125625

Offset: 1

Asher Auel, Sep 03 2000

For most values (except 9,2025 and 99225) number of divisors of n = sum of digits of n, see A057531.
The above comment is wrong: for 16 out of the first 34 terms of the sequence, the number of divisors of n does not equal the sum of the digits of n. - Harvey P. Dale, Dec 31 2015
Since A000005(n) is odd, n must be a square. - Robert Israel, Oct 31 2019

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

Cf. A000005, A005349, A033950, A057529.

[k:k in [1..6000001 by 2]| IsIntegral(k/NumberOfDivisors(k)) and IsIntegral(k/&+Intseq(k))]; // Marius A. Burtea, Oct 31 2019

filter:= proc(m) local n;
  n:= m^2;
  n mod numtheory:-tau(n) = 0 and n mod convert(convert(n,base,10),`+`) = 0
end proc:
map(`^`, select(filter, [seq(i,i=1..10000,2)]),2); # Robert Israel, Oct 31 2019

Select[Range[1,5*10^6,2],Divisible[#,DivisorSigma[0,#]] && Divisible[ #,Total[ IntegerDigits[#]]]&] (* Harvey P. Dale, Dec 31 2015 *)

More terms from Harvey P. Dale, Dec 31 2015

cp's OEIS Frontend

A057530 n is odd and divisible by number of divisors of n and sum of digits of n.

Views

Author

Keywords

Comments

Links

Crossrefs

Programs

Magma

Maple

Mathematica

Extensions