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A283147 Number n such that there are no primes of the form sigma(n)/k where 1 < k < n is a (proper) nondivisor of n. 0
1, 2, 4, 9, 12, 16, 25, 48, 64, 112, 192, 240, 289, 448, 729, 960, 1344, 1681, 1984, 2401, 3481, 4096, 5041, 6720, 7921, 10201, 12288, 15625, 17161, 27889, 28561, 28672, 29929, 39270, 53130, 61440, 65536, 71610, 82110 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Table of n, a(n) for n=1..39.

PROG

(PARI) is(n)=my(s=sigma(n), p=factor(s)[, 1], k); for(i=1, #p, k=s/p[i]; if(k<n&&n%k, return(0))); 1 \\ Charles R Greathouse IV, Mar 01 2017

CROSSREFS

Supersequence of A023194, A019279 and A061652.

Cf. A000203, A173540.

Sequence in context: A182859 A341239 A088901 * A111302 A241200 A092530

Adjacent sequences:  A283144 A283145 A283146 * A283148 A283149 A283150

KEYWORD

nonn

AUTHOR

Juri-Stepan Gerasimov, Mar 01 2017

EXTENSIONS

Corrected by Charles R Greathouse IV, Mar 01 2017

STATUS

approved

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Last modified July 26 20:34 EDT 2021. Contains 346295 sequences. (Running on oeis4.)