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A057530 n is odd and divisible by number of divisors of n and sum of digits of n. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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

LINKS

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

MAPLE

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

MATHEMATICA

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

PROG

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

CROSSREFS

Cf. A000005, A005349, A033950, A057529.

Sequence in context: A110260 A036896 A120319 * A014736 A017558 A159939

Adjacent sequences:  A057527 A057528 A057529 * A057531 A057532 A057533

KEYWORD

nonn,easy,base

AUTHOR

Asher Auel (asher.auel(AT)reed.edu), Sep 03 2000

EXTENSIONS

More terms from Harvey P. Dale, Dec 31 2015

STATUS

approved

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Last modified January 19 18:25 EST 2020. Contains 331051 sequences. (Running on oeis4.)