A391617 Numbers k whose abundance is 54: sigma(k) - 2*k = 54.

90, 4672, 116992, 2040832, 535969792, 2198965583872, 2417851639168785209884672

Offset

1,1

Comments

If 2^x-55 is prime, then 2^(x-1)*(2^x-55) is a term of this sequence. Large terms of this form: 618970019641722567217119232 (x=45), 649037107316852462774394019643392 (x=55), 166153499473114468260305194190897152 (x=59), and 46768052394588893382517648683240741410571406016512 (x=83).

Links

Table of n, a(n) for n=1..7.

Prog

(PARI) is(n) = sigma(n)-2*n == 54;

Crossrefs

Cf. A000203, A033879, A088831.

Sequence in context: A017753 A221893 A197194 * A281580 A369144 A111599

Adjacent sequences: A391614 A391615 A391616 * A391618 A391619 A391620

Keyword

nonn,more

Author

Alexander Violette, Jan 15 2026

Extensions

a(6)-a(7) confirmed and then added by Max Alekseyev, Feb 22 2026

Status

approved