A358022 Least odd number m such that m*2^n is an amicable number, and -1 if no such number exists.

12285, 605, 55, 779, 1081, 37, 119957, 73153, 2927269, 239, 25329329, 7230607, 964119281, 66445153, 7613527, 18431675687, 328796066369, 264003743, 11298797322497, 59592560831, 949755039781, 2759891672513

Offset

0,1

Comments

Similar to A358320 but restricted to amicable numbers.

Links

Table of n, a(n) for n=0..21.

Sergei Chernykh, Amicable Numbers.

Prog

(PARI) f(m) = if (m, sigma(m)-m, 0);
fpm(p, m) = (2*p-1)*sigma(m) - p*m;
a(n) = my(p=2^n); forstep(m=1, +oo, 2, my(x=fpm(p, m)); if ((x!=p*m) && (f(x) == p*m), return(m)));

Crossrefs

Cf. A001065, A002025, A259180, A262625, A358320.

Sequence in context: A254478 A186046 A358320 * A262625 A262623 A140688

Adjacent sequences: A358019 A358020 A358021 * A358023 A358024 A358025

Keyword

nonn,more

Author

Michel Marcus, Nov 17 2022

Extensions

a(12)-a(22) were calculated using Chernykh's database by Amiram Eldar, Nov 17 2022

Status

approved