login
This site is supported by donations to The OEIS Foundation.
Logo

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A081641 a(n) = n-th prime of class 13- according to the Erdos-Selfridge classification. 6
36449279, 53065907, 59681213, 69096887, 132756479, 135388367, 164255999, 179043637, 188991053, 207290663, 241560239, 279709259, 309550999, 364492781, 372993983, 377982103, 398007431, 406165099, 425633717, 445901987, 447609067, 516737983 (list; graph; refs; listen; history; internal format)
OFFSET

1,1

REFERENCES

R. K. Guy, Unsolved Problems in Number Theory, A18.

LINKS

M. F. Hasler, Table of n, a(n) for n=1..1641

MATHEMATICA

PrimeFactors[n_Integer] := Flatten[ Table[ #[[1]], {1}] & /@ FactorInteger[n]]; f[n_Integer] := Block[{m = n}, If[m == 0, m = 1, While[ IntegerQ[m/2], m /= 2]; While[ IntegerQ[m/3], m /= 3]]; Apply[Times, PrimeFactors[m] - 1]]; ClassMinusNbr[n_] := Length[ NestWhileList[f, n, UnsameQ, All]] - 3; Prime[ Select[ Range[23733333], ClassMinusNbr[ Prime[ # ]] == 12 &]]

PROG

(PARI) A081641 = nextclassminus(A081640) /* cf. A081640 */ - M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Apr 05 2007

CROSSREFS

Cf. A005113, A005105, A005106, A005107, A005108, A081633, A081633, A081635, A081636, A081637, A081638.

Cf. A056637, A081640, A129248.

Sequence in context: A183593 A183755 A105296 * A204852 A028965 A034645

Adjacent sequences:  A081638 A081639 A081640 * A081642 A081643 A081644

KEYWORD

nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 23 2003

EXTENSIONS

Edited by N. J. A. Sloane (njas(AT)research.att.com), May 14 2008 at the suggestion of R. J. Mathar.

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
Recent Additions | More pages | Superseeker | Maintained by The OEIS Foundation Inc.

Content is available under The OEIS End-User License Agreement .

Last modified February 17 15:44 EST 2012. Contains 206050 sequences.