A063788 Numbers k such that sigma(k) = 2k + Omega(k), where Omega(n) is the number of prime divisors of n (with repetition).

18, 88, 4030, 5830, 518656, 13174976, 134094848, 2146926592

Offset

1,1

Comments

From Donovan Johnson_, Dec 19 2008: (Start)

a(9) <= 2251798907715584.

a(10) <= 633825300114085990300727115776.

a(11) <= 2596148429267411760623818083663872. (End)

a(9) > 10^13. - Giovanni Resta, Jul 13 2015

Links

Table of n, a(n) for n=1..8.

Formula

Numbers k such that A000203(k) = 2k + A001222(k). - Wesley Ivan Hurt, Oct 30 2022

Prog

(PARI) for(n=1, 10^8, if(sigma(n)==2*n+bigomega(n), print(n)))

Crossrefs

Cf. A000203 (sigma), A001222 (Omega).

Sequence in context: A250101 A141842 A215191 * A066854 A247901 A369419

Adjacent sequences: A063785 A063786 A063787 * A063789 A063790 A063791

Keyword

more,nonn

Author

Jason Earls, Aug 16 2001

Extensions

a(7)-a(8) from Donovan Johnson, Dec 19 2008

Status

approved