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

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A085515 Order of first occurrence of a sequence of exactly n consecutive primes of the form 6*k+1. 3
 1, 2, 3, 6, 4, 5, 7, 8, 10, 11, 9, 13, 12, 15, 16, 14, 17, 18, 21, 19, 20, 23, 22, 25, 24, 26, 31, 27, 28, 30, 29, 32, 34, 33, 35 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS This sequence gives the index of A055625(n) after sorting by increasing magnitude. LINKS J. K. Andersen, Consecutive Congruent Primes. Hugo Pfoertner, Record producing runs of primes of the forms 6k+-1 Hugo Pfoertner, FORTRAN function ISPRIM to check primality. EXAMPLE a(3)=3, a(4)=6, a(5)=4 because the first occurrence of exactly 6 consecutive primes of the form 6*k+1 (1741,1747,1753,1759,1777,1783) occurs after the first occurrence of 3 consecutive primes of this form (151,157,163) and before the first occurrence of 4 consecutive "6k+1"-primes (3049,3061,3067,3079). MATHEMATICA (* Program not suitable to compute a large number of terms. *) pp = Table[{p = Prime[n], Mod[p, 6]}, {n, 10^7}]; sp = Split[pp, Mod[#1[[2]], 6] == Mod[#2[[2]], 6]&]; b[n_] := SelectFirst[sp, Length[#] == n && MatchQ[#, {{_Integer, 1} ..}]& ][[1, 1]]; Sort[Table[{b[n], n}, {n, 1, 16}]][[All, 2]] (* Jean-François Alcover, Nov 21 2018 *) PROG FORTRAN program given at link. CROSSREFS Cf. A055625, A085516 (sorted occurrence of first runs of "6k-1" primes). Sequence in context: A213625 A132368 A157248 * A082354 A130344 A122344 Adjacent sequences:  A085512 A085513 A085514 * A085516 A085517 A085518 KEYWORD more,nonn AUTHOR Hugo Pfoertner, Jul 31 2003 EXTENSIONS More terms from Herman Jamke (hermanjamke(AT)fastmail.fm), Oct 27 2006 a(32)-a(35) from Giovanni Resta, Aug 04 2013 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 November 30 13:47 EST 2021. Contains 349420 sequences. (Running on oeis4.)