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!)
A076565 Greatest prime divisor of 2n+1 (sum of two successive integers). 6
3, 5, 7, 3, 11, 13, 5, 17, 19, 7, 23, 5, 3, 29, 31, 11, 7, 37, 13, 41, 43, 5, 47, 7, 17, 53, 11, 19, 59, 61, 7, 13, 67, 23, 71, 73, 5, 11, 79, 3, 83, 17, 29, 89, 13, 31, 19, 97, 11, 101, 103, 7, 107, 109, 37, 113, 23, 13, 17, 11, 41, 5, 127, 43, 131, 19, 5, 137, 139, 47, 13 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A006530(2n+1). - Robert Israel, Mar 17 2017

MAPLE

seq(max(numtheory:-factorset(2*n+1)), n=1..200); # Robert Israel, Mar 17 2017

MATHEMATICA

Table[FactorInteger[2n + 1][[-1, 1]], {n, 1, 100}] (* Indranil Ghosh, Mar 20 2017 *)

PROG

(PARI) for(n=1, 100, print1(vecmax(factor(2*n + 1)[, 1]), ", ")) \\ Indranil Ghosh, Mar 20 2017

(Python)

from sympy.ntheory import primefactors

print [max(primefactors(2*n + 1)) for n in range(1, 101)] # Indranil Ghosh, Mar 20 2017

CROSSREFS

Cf. A006530

Sequence in context: A090368 A120374 A088836 * A286517 A199423 A100029

Adjacent sequences:  A076562 A076563 A076564 * A076566 A076567 A076568

KEYWORD

easy,nonn

AUTHOR

Zak Seidov, Oct 19 2002

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 February 16 16:00 EST 2020. Contains 331961 sequences. (Running on oeis4.)