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A075494 Squares whose sum of digits exceeds the number of divisors. 0
4, 9, 16, 25, 49, 64, 81, 121, 169, 196, 256, 289, 361, 484, 529, 625, 676, 729, 784, 841, 961, 1089, 1156, 1225, 1369, 1444, 1681, 1849, 1936, 2116, 2209, 2401, 2809, 3025, 3249, 3364, 3481, 3721, 3844, 3969, 4096, 4225, 4489, 4624, 4761, 5041, 5329 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..47.

FORMULA

Numbers k^2 such that A007953(k^2) > A000005(k^2).

EXAMPLE

Sequence consists mainly of squares of primes and of special composites like 33, 34, 35, 38, 44, 46.

MATHEMATICA

sud[x_] := Apply[Plus, IntegerDigits[x]] Do[s=sud[n]-DivisorSigma[0, n]; If[Greater[s, 0]&&IntegerQ[Sqrt[n]], Print[n]], {n, 1, 10000}]

Select[Range[80]^2, Total[IntegerDigits[#]]>DivisorSigma[0, #]&] (* Harvey P. Dale, Feb 16 2020 *)

CROSSREFS

Cf. A007953, A000005, A057531, A075491-A075493.

Sequence in context: A188061 A279456 A069560 * A063735 A056798 A036454

Adjacent sequences:  A075491 A075492 A075493 * A075495 A075496 A075497

KEYWORD

base,nonn

AUTHOR

Labos Elemer, Sep 26 2002

EXTENSIONS

Edited by Jon E. Schoenfield, Sep 23 2018

STATUS

approved

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Last modified April 1 02:10 EDT 2020. Contains 333153 sequences. (Running on oeis4.)