login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A324256 Larger of super amicable pair m < n defined by sigma(sigma(m)) = sigma(sigma(n)) = m + n. 2
37, 28201, 34687, 65587, 2089951, 4091797, 8340613, 8161477, 10124833, 18927067, 37179433, 37393633, 25855567, 64346413, 107160373, 95150203, 159440893, 238973101, 257658061, 277743397, 322210813, 256268149, 349883707, 578403913, 814865497, 752724457, 704710543 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The terms are ordered according to the their lesser counterparts (A324255).

Analogous to A002046 as A019279 is analogous to A000396.

LINKS

Table of n, a(n) for n=1..27.

EXAMPLE

(23, 37) are the first pair since sigma(sigma(23)) = sigma(sigma(37)) = 60 = 23 + 37.

MATHEMATICA

seq={}; s[n_]:=DivisorSigma[1, DivisorSigma[1, n]]-n; Do[m=s[n]; If[m>n && s[m]==n, AppendTo[seq, m]], {n, 1, 60000}]; seq

PROG

(PARI) f(n) = sigma(sigma(n)) - n;

lista(nn) = {for (n=1, nn, my(fn = f(n)); if ((fn > n) && (f(fn) == n), print1(fn, ", ")); ); } \\ Michel Marcus, Feb 20 2019

CROSSREFS

Cf. A000203, A000396, A002046, A019279, A045614 (unitary analog), A051027, A324255.

Sequence in context: A202794 A129054 A129053 * A096349 A015061 A015037

Adjacent sequences:  A324253 A324254 A324255 * A324257 A324258 A324259

KEYWORD

nonn

AUTHOR

Amiram Eldar, Feb 19 2019

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified November 29 04:04 EST 2021. Contains 349416 sequences. (Running on oeis4.)