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!)
A083284 Numbers m such that m and m+2 are both brilliant numbers, where brilliant numbers are semiprimes whose prime factors have an equal number of decimal digits, or whose prime factors are equal. 2
4, 527, 779, 869, 899, 1079, 1157, 1271, 1679, 4187, 6497, 6887, 24287, 24881, 25019, 29591, 35237, 37127, 37769, 38807, 39269, 39911, 41309, 43361, 44831, 45347, 46001, 46127, 47261, 48509, 48929, 51809, 52907, 54389, 55481, 55751, 55961 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The only consecutive brilliant numbers are {9, 10} and {14, 15}; and for m > 14 there are no brilliant constellations of the form {m, m+(2k+1)} or equivalently {n, 2k+m+1} with k >= 0. Proof: One of m and 2k+m+1 will be even. And there are no even brilliant numbers > 14 since they must have the form 2*p where p is a prime having only one digit.

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

EXAMPLE

a(3) = 779 because 779=19*41 and 781=11*71.

CROSSREFS

Cf. A078972.

Sequence in context: A003393 A089668 A257922 * A350613 A152218 A152463

Adjacent sequences:  A083281 A083282 A083283 * A083285 A083286 A083287

KEYWORD

base,easy,nonn

AUTHOR

Jason Earls, Jun 03 2003

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 October 4 21:22 EDT 2022. Contains 357240 sequences. (Running on oeis4.)