

A113286


Let S(n)=1/4*Sigma(n) . Numbers such that S(S(n))=n, 1/4Sociable number of order 1 or 2.


1



30240, 32760, 859320, 898560, 2096640, 2178540, 2234232, 23569920, 45532800, 54996480, 61281792, 142990848, 422688000, 436205952, 1379454720
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

a(1) and a(2) are 4 multiple perfect numbers (A027687). a(4)=S(a(3)).
a(6), a(8), a(9), a(12), and a(15) are also 4 multiple perfect numbers (A027687).  Michel Marcus, Feb 23 2014


LINKS

Table of n, a(n) for n=1..15.
Eric Weisstein's World of Mathematics, Sociable Numbers


PROG

(PARI) isok(n) = (type(s= sigma(n)/4) == "t_INT") && (sigma(s)/4 == n); \\ Michel Marcus, Feb 20 2014


CROSSREFS

Cf. A113546.
Sequence in context: A255752 A254841 A247855 * A027687 A190475 A218029
Adjacent sequences: A113283 A113284 A113285 * A113287 A113288 A113289


KEYWORD

nonn,more


AUTHOR

Yasutoshi Kohmoto, Jan 27 2006


EXTENSIONS

a(5)a(15) added by Michel Marcus, Feb 24 2014


STATUS

approved



