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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A171603 Lesser of two consecutive primes such that half-sums are product of two distinct primes. 0
5, 13, 19, 23, 31, 37, 67, 83, 89, 109, 127, 131, 199, 211, 251, 271, 307, 331, 379, 383, 389, 443, 449, 467, 487, 499, 509, 563, 661, 683, 719, 769, 797, 877, 929, 937, 971, 997, 1009, 1123, 1163, 1201, 1223, 1231, 1237, 1283, 1291, 1297, 1307, 1459, 1511 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..51.

EXAMPLE

(5+7)/2=6->2*3, (13+17)/2=15->3*5,..

MATHEMATICA

f[n_]:=Last/@FactorInteger[n]=={1, 1}; lst={}; Do[p=Prime[n]; q=Prime[n+1]; s=(p+q)/2; If[f[s], AppendTo[lst, p]], {n, 6!}]; lst

CROSSREFS

Cf. A171602

Sequence in context: A209663 A156111 A162174 * A118915 A084442 A023270

Adjacent sequences:  A171600 A171601 A171602 * A171604 A171605 A171606

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Dec 12 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 | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 11 17:52 EDT 2020. Contains 335626 sequences. (Running on oeis4.)