The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A104387 Larger of two successive primes the average of which is a repdigit. 4
 5, 7, 11, 101, 113, 4447, 111111113, 555555555559, 10000000000000061, 111111111111111131, 444444444444444469, 555555555555555555619, 777777777777777777777787, 333333333333333333333333333333373, 444444444444444444444444444444444497 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Lesser primes A104388, repdigits A104389. What is the next term? The next term is 444444444444444444444444444444444497. The first term with more than 100 digits is a(22) which has 109 digits. - Harvey P. Dale, Jun 28 2011 LINKS Michael S. Branicky, Table of n, a(n) for n = 1..31 FORMULA a(n) = prime(A104386(n)+1). MATHEMATICA Union[Flatten[Table[NextPrime/@Select[FromDigits/@Table[PadLeft[{i}, n, i], {n, 45}], Mean[{NextPrime[#], NextPrime[#, -1]}]==#&], {i, 9}]]] (* Harvey P. Dale, Jun 28 2011 *) PROG (Python) from itertools import count, islice from sympy import isprime, prevprime def agen(): for d in count(1): ru = int("1"*d) for r in range(ru, 10*ru, ru): if r > 2: p = prevprime(r) if isprime(r + (r-p)) and prevprime(r+(r-p)) == p: yield 2*r - p print(list(islice(agen(), 15))) # Michael S. Branicky, Jun 30 2022 CROSSREFS Cf. A054268, A104386, A104388, A104389. Sequence in context: A027728 A218275 A086140 * A133761 A057659 A098040 Adjacent sequences: A104384 A104385 A104386 * A104388 A104389 A104390 KEYWORD nonn,base AUTHOR Zak Seidov, Mar 04 2005 EXTENSIONS More terms from Giovanni Resta, Apr 05 2006 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.

Last modified May 21 19:35 EDT 2024. Contains 372738 sequences. (Running on oeis4.)