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

Author

Michel Marcus, Nov 17 2022

Keywords

• nonn
• more

Comments

Similar to A358320 but restricted to amicable numbers.

Links

• Sergei Chernykh, Amicable Numbers.

Crossrefs

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

Programs

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)));

Extensions

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