A324256 - OEIS

A324256

Larger of super amicable pair m < n defined by sigma(sigma(m)) = sigma(sigma(n)) = m + n.

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

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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