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!)
A176087 Numbers n such that (10^n-1)/3 * 10^ceiling(log_10(n+1)) + n is prime. 3
1, 253, 35473 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
No term is a multiple of 2, 3, or 5. The decimal expansion of each corresponding prime is n 3's with n's decimal expansion concatenated. Probable primes found by PrimeForm. Prime for 253 proved by Primo. No more terms up to 50000.
LINKS
EXAMPLE
The first term is 1 because 31 is prime.
PROG
(PARI) is(n)=ispseudoprime((10^n-1)/3 * 10^logint(10*n, 10) + n) \\ Charles R Greathouse IV, May 22 2017
CROSSREFS
Cf. A070746 (n 1's followed by n is prime), A084428 (n 7's followed by n is prime), A174710, A004218.
Sequence in context: A242463 A271985 A255182 * A006060 A077695 A253880
KEYWORD
bref,more,nonn
AUTHOR
Rick L. Shepherd, Apr 08 2010
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 March 3 16:27 EST 2024. Contains 370512 sequences. (Running on oeis4.)