A282049 Least prime p such that n divides sigma(p*n).

2, 3, 2, 3, 19, 5, 13, 7, 17, 19, 43, 2, 103, 2, 19, 31, 67, 5, 37, 19, 41, 43, 137, 5, 149, 103, 53, 3, 173, 19, 61, 31, 43, 67, 139, 71, 73, 37, 233, 3, 163, 13, 257, 43, 29, 137, 281, 11, 97, 149, 67, 103, 211, 17, 109, 13, 113, 173, 353, 2, 487, 61, 251, 127, 389, 43, 401, 67

Offset

1,1

Comments

a(n) <= A038700(n). Numbers n such that a(n) is not equal to A038700(A017666(n)) are 6, 14, 24, 28, 60, 78, 84, 90, 120, 234, 248, 270, 336, 496, 532, 546, ...

Links

Altug Alkan, Table of n, a(n) for n = 1..30000

Example

a(5) = 19 because 5 divides sigma(19*5) = 120 and 19 is the least prime number with this property.

Prog

(PARI) a(n) = {my(p=2); while (sigma(p*n) % n != 0, p = nextprime(p+1)); p; } \\ David A. Corneth, Feb 05 2017

Crossrefs

Cf. A000203, A227470

Sequence in context: A109620 A138781 A224416 * A038700 A177799 A125767

Adjacent sequences: A282046 A282047 A282048 * A282050 A282051 A282052

Keyword

nonn

Author

Altug Alkan, Feb 05 2017

Status

approved