A206026 a(n) = smallest number m such that sigma(k) = m has at least n positive solutions k.

1, 12, 24, 72, 72, 168, 240, 336, 360, 504, 576, 720, 720, 720, 720, 1440, 1440, 1440, 1440, 1440, 1440, 2880, 2880, 2880, 2880, 2880, 2880, 2880, 2880, 4320, 4320, 4320, 4320, 4320, 4320, 5760, 5760, 8640, 8640, 8640, 8640, 8640, 8640, 8640, 8640, 8640, 8640

Offset: 1

Author

Jaroslav Krizek, Feb 03 2012

Keywords

• nonn

Comments

Sequence of numbers from A145899.

Examples

			a(6) = 168 because 168 is the smallest value of sigma(k) for n = 6 positive integers k such that sigma(k) = 168 has solution; k = 60, 78, 92, 123, 143, 167.
		

Links

• Amiram Eldar, Table of n, a(n) for n = 1..1000
• Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems (invphi.gp).

Crossrefs

Cf. A000203, A054973, A085790, A145899, A206027.

Programs

PARI

list(len) = {my(v = vector(len), k = 1, c = 0, i); while(c < len, i = invsigmaNum(k); for(j = 1, i, if(j <= len && v[j] == 0, v[j] = k; c++)); k++); v;} \\ Amiram Eldar, Dec 15 2024, using Max Alekseyev's invphi.gp