The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A206553 Least prime p > 3 such that 2^n + p*2^floor((n+1)/2) - 1 is prime. 2
 5, 5, 13, 7, 5, 5, 7, 7, 11, 13, 13, 11, 5, 11, 37, 11, 5, 23, 13, 47, 89, 13, 19, 19, 11, 7, 19, 23, 17, 13, 19, 43, 29, 79, 61, 17, 191, 43, 337, 53, 29, 17, 13, 13, 29, 11, 19, 11, 11, 13, 43, 163, 29, 13, 7, 53, 23, 97, 31, 29, 41, 83, 79, 23, 191, 97 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Pierre CAMI, Table of n, a(n) for n = 1..10000 EXAMPLE 2^1+5*2^1-1 = 11 prime so a(1) = 5. 2^2+5*2^1-1 = 13 prime so a(2) = 5. PROG PFGW64 from Primeform group and SRYPTIFY command : pfgw64 -f in.txt in.txt file : SCRIPT DIM kk DIM nn, 0 DIM mm DIMS tt OPENFILEOUT myfil, prem.txt LABEL loopn SET nn, nn+1 IF nn>10000 THEN END IF nn%2==0 THEN SET mm, nn/2 IF nn%2==1 THEN SET mm, nn/2+1 SET kk, 2 LABEL loopk SET kk, kk+1 SETS tt, %d, %d, %d, %d\ ; nn; kk; p(kk); mm PRP (2^(nn-mm)+p(kk))*2^mm-1, tt IF ISPRP THEN GOTO a IF ISPRIME THEN GOTO a GOTO loopk LABEL a WRITE myfil, tt GOTO loopn (Haskell) a206553 n = head [p | p <- drop 2 a000040_list, a010051 (2^n + p*2^(div (n+1) 2) - 1) == 1] -- Reinhard Zumkeller, Feb 10 2012 CROSSREFS Cf. A206554. Cf. A010051, A000040. Sequence in context: A338085 A302676 A339947 * A122213 A224067 A049735 Adjacent sequences: A206550 A206551 A206552 * A206554 A206555 A206556 KEYWORD nonn AUTHOR Pierre CAMI, Feb 09 2012 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 January 29 23:01 EST 2023. Contains 359939 sequences. (Running on oeis4.)