The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A060254 Primes which are the sum of two consecutive composite numbers. 22
 17, 19, 29, 31, 41, 43, 53, 67, 71, 79, 89, 97, 101, 103, 109, 113, 127, 131, 137, 139, 149, 151, 163, 173, 181, 191, 197, 199, 211, 223, 229, 233, 239, 241, 251, 257, 269, 271, 281, 283, 293, 307, 311, 317, 331, 337, 349, 353, 367, 373, 379, 389, 401, 409 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS For the smaller of the consecutive composite pair (p-+1)/2, see A096784 This sequence also contains exactly those odd primes p where neither p-1 nor p+1 is the product of exactly 2 (not necessarily distinct) primes. - Leroy Quet, Sep 09 2008 5 together with the prime numbers A060254=(5,17,19,29,31,41,43,53,..)=primes which are the sum of two consecutive nonprime numbers. - Juri-Stepan Gerasimov, Aug 30 2009 Conjecture: a(n) ~ n log n. - Charles R Greathouse IV, Apr 29 2015 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 EXAMPLE The prime 19 is an entry since it is the sum of 9=3^2 and 10=2*5. MATHEMATICA 2Select[ Range[210], PrimeQ[ # ] == PrimeQ[ # + 1] == False && PrimeQ[2# + 1] == True &] + 1 Select[Total/@Partition[Select[Range[300], CompositeQ], 2, 1], PrimeQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jan 12 2019 *) PROG (PARI) is(n)=!isprime(n\2) && !isprime(n\2+1) && isprime(n) \\ Charles R Greathouse IV, Apr 29 2015 CROSSREFS Cf. A096783, A096784, A096785, A096786, A096787, A096788, A096677. Sequence in context: A175384 A053689 A176462 * A190792 A137796 A125213 Adjacent sequences:  A060251 A060252 A060253 * A060255 A060256 A060257 KEYWORD nonn AUTHOR Robert G. Wilson v, Mar 22 2001 STATUS approved

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

Last modified June 24 05:09 EDT 2021. Contains 345416 sequences. (Running on oeis4.)