A260508 Numbers k such that A000203(k) = k*A001221(k).

6, 28, 120, 496, 672, 8128, 30240, 33550336, 8589869056, 137438691328, 2305843008139952128, 2658455991569831744654692615953842176, 191561942608236107294793378084303638130997321548169216, 13164036458569648337239753460458722910223472318386943117783728128

Offset: 1

Author

Felix Fröhlich, Jul 27 2015

Keywords

• nonn

Comments

a(n) is in A000396 iff A001221(a(n)) == 2, i.e., if a(n) is in A007774.

a(11) > 2.5*10^12. - Giovanni Resta, Jul 28 2015

Links

• Amiram Eldar, Table of n, a(n) for n = 1..15

Crossrefs

Subsequence of A007691.

Cf. A000203, A000396, A001221, A007774.

Programs

PARI

is(n) = sigma(n)==n*omega(n)

Extensions

a(9)-a(10) from Giovanni Resta, Jul 28 2015

a(11)-a(14) from Amiram Eldar, May 09 2024