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 A020477 Sum of divisors of n is a cube. 22
 1, 7, 102, 110, 142, 159, 187, 381, 690, 714, 770, 994, 1034, 1054, 1065, 1113, 1164, 1173, 1265, 1293, 1309, 1633, 1643, 2667, 3638, 3937, 4505, 4830, 4855, 5373, 5671, 5730, 5997, 6486, 6517, 6906, 7130, 7238, 7378, 7455, 7755, 7905, 8148, 8211, 8426 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 REFERENCES David Wells, Curious and Interesting Numbers (Revised), Penguin Books, page 118. LINKS T. D. Noe and K. D. Bajpai, Table of n, a(n) for n = 1..10800 (first 1000 terms from T. D. Noe) 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. C. Nelson, D. E. Penney, and C. Pomerance (1974) 714 and 715, J. Recreational Mathematics 7(2), 87-89 (see top of page 89); alternative copy. [Warning: As of March 2018 this site appears to have been hacked. Proceed with great caution. The original content should be retrieved from the Wayback machine and added here. - N. J. A. Sloane, Mar 29 2018] EXAMPLE Factor 381; divisors are 1, 3, 127, 381. Sum is 512. Integral cube root of n is 8. So 381 is in sequence. MATHEMATICA Do[If[IntegerQ[DivisorSigma[1, n]^(1/3)], Print[n]], {n, 1, 10^4}] Select[Range[10000], IntegerQ[Surd[DivisorSigma[1, #], 3]]&] (* Harvey P. Dale, Nov 16 2014 *) PROG (PARI) isok(n) = ispower(sigma(n), 3); \\ Michel Marcus, Jul 03 2014 CROSSREFS Cf. A006532. Sequence in context: A175345 A142358 A210684 * A203356 A223239 A140633 Adjacent sequences:  A020474 A020475 A020476 * A020478 A020479 A020480 KEYWORD nonn AUTHOR STATUS approved

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Last modified July 21 06:55 EDT 2019. Contains 325192 sequences. (Running on oeis4.)