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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
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
Sequence in context: A237104 A156402 A139676 * A235424 A235420 A236281
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 May 30 01:30 EDT 2024. Contains 372954 sequences. (Running on oeis4.)