A309553 Imperfect numbers of the form 2^(2^k-1)*F_1*F_2*...*F_(k-1), where F is a Fermat number.

40, 10880, 715816960, 3074457344902430720

Offset

1,1

Comments

Numbers of this form are imperfect only for k = 2, 3, 4, 5.

Links

Table of n, a(n) for n=1..4.

László Tóth, A survey of the alternating sum-of-divisors function, arXiv:1111.4842 [math.NT], 2011-2014, end of section 8.

László Tóth, A survey of the alternating sum-of-divisors function, Acta Universitatis Sapientiae, Mathematica, Vol. 5, No. 1 (2013), pp. 93-107.

Example

For k=2, 2^3*F_1 = 8*5 = 40, so 40 is in the sequence.

Crossrefs

Cf. A000215, A127724.

Sequence in context: A364517 A184892 A119525 * A123381 A210347 A221391

Adjacent sequences: A309550 A309551 A309552 * A309554 A309555 A309556

Keyword

nonn,fini,full

Author

Jud McCranie, Aug 07 2019

Status

approved