login
A143986
Smallest number d such that the smallest number with d divisors is a multiple of n.
0
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
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: A096780 A376904 A332454 * A059662 A259630 A114883
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