A019422 Numbers whose sum of divisors is a fourth power.

1, 217, 510, 642, 710, 742, 782, 795, 862, 935, 1177, 1207, 1219, 2667, 3937, 7590, 7854, 8743, 9481, 9798, 9858, 10810, 10934, 11186, 11235, 11510, 11594, 11715, 11985, 12082, 12243, 12903, 12945, 13022, 13462, 13587, 13685, 13822, 14223, 15085

Offset

1,2

References

J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 217, p. 62, Ellipses, Paris 2008.

Links

Donovan Johnson, Table of n, a(n) for n = 1..1000

Frits Beukers, Florian Luca and Frans Oort, Power Values of Divisor Sums, The American Mathematical Monthly, Vol. 119, No. 5 (May 2012), pp. 373-380.

Mathematica

Select[Range[16000], IntegerQ[Power[DivisorSigma[1, #], (4)^-1]]&] (* Harvey P. Dale, Jan 22 2012 *)

Prog

(PARI) c=0; for(n=1, 8240486, if(ispower(sigma(n), 4), c++; write("b019422.txt", c " " n))) /* Donovan Johnson, Jun 13 2013 */

Crossrefs

Sequence in context: A145732 A038594 A020232 * A231558 A101826 A262052

Adjacent sequences: A019419 A019420 A019421 * A019423 A019424 A019425

Keyword

nonn

Author

David W. Wilson

Status

approved