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!)
 A235859 Define a(4)=3, then a(n+1) is the smallest prime P such that a(n) <= P < 2*n with 2*n-P=Q prime and, if not possible, a(n+1) is the smallest prime P such that P < a(n) < 2*n with 2*n-P=Q prime. 1
 3, 3, 5, 11, 11, 11, 13, 17, 17, 19, 23, 23, 29, 29, 29, 31, 37, 37, 37, 41, 41, 43, 47, 47, 53, 53, 53, 59, 59, 59, 61, 67, 67, 67, 71, 71, 73, 79, 79, 79, 83, 83, 89, 89, 89, 19, 29, 29, 31, 47, 47, 67, 71, 71, 73, 89, 89, 103, 107, 107, 109, 113, 113 (list; graph; refs; listen; history; text; internal format)
 OFFSET 4,1 LINKS Pierre CAMI, Table of n, a(n) for n = 4..10005 EXAMPLE a(4)=3 as 2*4-3=5 prime by definition a(5)=3 as 2*5-3=7 prime, a(5)=a(4), a(5)<5 a(6)=5 as 2*6-5=7 prime, a(6)>a(5), a(6)<6 a(7)=5 not possible as 14-5=9 composite a(7)=7 not possible as 7=7 a(7)=11 as 2*7-11=3 prime ......................... a(48)=89 as 2*48-89=7 prime a(49)=89 not possible as 2*49-89=9 composite a(49)=97 not possible as 2*49-97=unity a(49)=19 as 19 is the smallest prime such that 2*49-19 is prime a(50)=29 as 29 is the smallest prime >=19 such that 2*50-29 is prime PROG (PFGW & SCRIPT) SCRIPT DIM n, 3 DIM i DIM pp DIMS t OPENFILEOUT myf, a(n).txt LABEL loop1 OPENFILEIN maf, prime.txt GETNEXT i, maf GETNEXT i, maf LABEL a SET n, n+1 IF n>10005 THEN END SET pp, 2*n-i SETS t, %d, %d\,; n; i PRP pp, t IF ISPRP THEN GOTO c LABEL b GETNEXT i, maf IF i==n THEN GOTO b IF 2*n-i<3 THEN GOTO d SET pp, 2*n-i SETS t, %d, %d\,; n; i PRP pp, t IF ISPRP THEN GOTO c GOTO b LABEL c WRITE myf, t GOTO a LABEL d CLOSEFILE maf SET n, n-1 GOTO loop1 CROSSREFS Cf. A002373, A020483, A235649. Sequence in context: A132751 A218354 A286514 * A279790 A338847 A032020 Adjacent sequences:  A235856 A235857 A235858 * A235860 A235861 A235862 KEYWORD nonn,less AUTHOR Pierre CAMI, Jan 16 2014 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 September 21 00:14 EDT 2021. Contains 347596 sequences. (Running on oeis4.)