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.

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

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