A260508 - OEIS

%I #16 May 09 2024 02:52:46

%S 6,28,120,496,672,8128,30240,33550336,8589869056,137438691328,

%T 2305843008139952128,2658455991569831744654692615953842176,

%U 191561942608236107294793378084303638130997321548169216,13164036458569648337239753460458722910223472318386943117783728128

%N Numbers k such that A000203(k) = k*A001221(k).

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

%C a(11) > 2.5*10^12. - _Giovanni Resta_, Jul 28 2015

%H Amiram Eldar, <a href="/A260508/b260508.txt">Table of n, a(n) for n = 1..15</a>

%o (PARI) is(n) = sigma(n)==n*omega(n)

%Y Subsequence of A007691.

%Y Cf. A000203, A000396, A001221, A007774.

%K nonn

%O 1,1

%A _Felix Fröhlich_, Jul 27 2015

%E a(9)-a(10) from _Giovanni Resta_, Jul 28 2015

%E a(11)-a(14) from _Amiram Eldar_, May 09 2024