A143986 Smallest number d such that the smallest number with d divisors is a multiple of n.

1, 2, 4, 3, 12, 4, 32, 5, 9, 12, 96, 6, 240, 32, 12, 5, 640, 9, 1280, 12, 32, 96, 2560, 8, 27, 240, 25, 32, 9600, 12, 19200, 7, 96, 640, 32, 9, 57344, 1280, 240, 16, 114688, 32, 229376, 96, 18, 2560, 458752, 10, 81, 27, 640, 240, 1290240, 25, 96, 32, 1280, 9600

Offset

1,2

Comments

Smallest number d such that A005179(d) is a multiple of n. - Iain Fox, Dec 09 2017

Links

Table of n, a(n) for n=1..58.

Example

a(5) = 12 because the smallest number with 12 divisors (60) is a multiple of 5. a(5) cannot be 8 because 24, which is not a multiple of 5, is the smallest number with 8 divisors.

Prog

(PARI) findsmd(n, vndiv) = {d = 1; while ( vndiv[d] % n, d++); d; }
lista(nn) = {v005179 = readvec("b005179.log"); for(n = 1, nn, print1(findsmd(n, v005179), ", "); ); } \\ Michel Marcus, Feb 11 2014

Crossrefs

Cf. A005179. - R. J. Mathar, Nov 02 2008

Sequence in context: A248981 A096780 A332454 * A059662 A259630 A114883

Adjacent sequences: A143983 A143984 A143985 * A143987 A143988 A143989

Keyword

nonn,hard

Author

J. Lowell, Sep 06 2008

Extensions

a(7)-a(22) from R. J. Mathar, Nov 02 2008

a(23)-a(58) from Iain Fox, Sep 14 2020

Status

approved