login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A155891 Least positive integer such that a(n)! starts with n, both written in binary. 6
1, 2, 3, 7, 6, 3, 5, 20, 7, 14, 6, 4, 10, 12, 5, 20, 27, 50, 7, 14, 23, 6, 13, 4, 25, 30, 10, 12, 51, 5, 63, 24, 20, 36, 27, 50, 59, 11, 7, 14, 26, 75, 23, 9, 6, 13, 49, 71, 144, 31, 25, 30, 199, 19, 10, 46, 12, 51, 83, 5, 28, 73, 63, 62, 24, 54, 20, 36, 67, 27, 40, 74, 50, 59, 124 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Nick Hobson, C program.
EXAMPLE
a(7) = 5 since 7 = 111_2 (i.e., written in base 2) and 5! = 1111000_2 is the least factorial to have 111 as its most significant binary digits.
PROG
(PARI) A155891(n)={ local( F=1, k=1 ); while( F\1!=n, F*=k++; while( F>=n+1, F/=2 )); k}
(C) See Links section.
CROSSREFS
Sequence in context: A092927 A071553 A021812 * A234026 A245443 A246265
KEYWORD
base,nonn
AUTHOR
M. F. Hasler, Feb 01 2009
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 14 16:43 EDT 2024. Contains 374322 sequences. (Running on oeis4.)