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!)
A252489 Index of the largest prime which divides n(n+1). 3
1, 2, 2, 3, 3, 4, 4, 2, 3, 5, 5, 6, 6, 4, 3, 7, 7, 8, 8, 4, 5, 9, 9, 3, 6, 6, 4, 10, 10, 11, 11, 5, 7, 7, 4, 12, 12, 8, 6, 13, 13, 14, 14, 5, 9, 15, 15, 4, 4, 7, 7, 16, 16, 5, 5, 8, 10, 17, 17, 18, 18, 11, 4, 6, 6, 19, 19, 9, 9, 20, 20, 21, 21, 12, 8, 8, 6 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Yields the row of A145605 in which n appears, and also the first row of A138180 in which n appears.

LINKS

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

FORMULA

a(n) = pi(A074399(n)), where pi = A000720.

a(n) = max(A061395(n),A061395(n+1)). - Robert Israel, Feb 12 2021

MAPLE

A061395:= [1, seq(numtheory:-pi(max(numtheory:-factorset(n))), n=2..101)]:

zip(max, A061395[1..-2], A061395[2..-1]); # Robert Israel, Feb 12 2021

PROG

(PARI) a(n)=primepi(vecmax(factor(n*(n+1))[, 1]))

CROSSREFS

Cf. A002071, A145604, A138180, A145605, A002072, A074399, A061395.

Sequence in context: A106747 A335979 A083447 * A332250 A340321 A340320

Adjacent sequences:  A252486 A252487 A252488 * A252490 A252491 A252492

KEYWORD

nonn,look

AUTHOR

M. F. Hasler, Jan 16 2015

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 27 01:32 EST 2021. Contains 341643 sequences. (Running on oeis4.)