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A291209 Numbers n such that psi(n) is the sum of proper divisors of n where psi(n) = A001615(n). 1
9504, 16560, 41400, 5048568, 10889856, 11941344, 16255080, 131473152, 5517818880, 107561120688, 612014161920 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Or numbers n such that sigma(n) = psi(n) + n where psi(n) = A001615(n) and sigma(n) = A000203(n).

9504 = 2^5*3^3*11 is the smallest number with this property.

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

16560 is a term because sigma(16560) = 58032 and psi(16560) = 41472; sigma(16560) - psi(16560) = 16560.

PROG

(PARI) a001615(n) = n*sumdivmult(n, d, issquarefree(d)/d);

isok(n) = sigma(n)==a001615(n)+n; \\ after Charles R Greathouse IV at A001615

CROSSREFS

Cf. A000203, A001065, A001615.

Sequence in context: A237104 A156402 A139676 * A235424 A235420 A236281

Adjacent sequences:  A291206 A291207 A291208 * A291210 A291211 A291212

KEYWORD

nonn,more

AUTHOR

Altug Alkan, Aug 21 2017

EXTENSIONS

a(9)-a(11) from Giovanni Resta, Aug 21 2017

STATUS

approved

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Last modified September 28 17:37 EDT 2022. Contains 357080 sequences. (Running on oeis4.)