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!)
A252494 Numbers n such that all prime factors of n and n+1 are <= 11. (Related to the abc conjecture.) 5
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 14, 15, 20, 21, 24, 27, 32, 35, 44, 48, 49, 54, 55, 63, 80, 98, 99, 120, 125, 175, 224, 242, 384, 440, 539, 2400, 3024, 4374, 9800 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

This sequence is complete by a theorem of Stormer, cf. A002071.

This is the 5th row of the table A138180. It has 40=A002071(5)=A145604(1)+...+ A145604(5) terms and ends with A002072(5)=9800. It is the union of all terms in rows 1 through 5 of the table A145605.

This is a subsequence of A252493, and contains A085152 and A085153 as subsequences.

LINKS

Table of n, a(n) for n=1..40.

OEIS Index entries for sequences related to the abc conjecture

MATHEMATICA

Select[Range[10000], FactorInteger[ # (# + 1)][[ -1, 1]] <= 11 &]

PROG

(PARI) for(n=1, 9e6, vecmax(factor(n++)[, 1])<12 && vecmax(factor(n--+(n<2))[, 1])<12 && print1(n", ")) \\ Skips 2 if n+1 is not 11-smooth: Twice as fast as the naive version.

CROSSREFS

Cf. A002071, A145604, A138180, A145605, A002072, A085152, A085153, A252493, A252492.

Sequence in context: A113191 A191923 A191922 * A030294 A125668 A034894

Adjacent sequences:  A252491 A252492 A252493 * A252495 A252496 A252497

KEYWORD

nonn,fini,full

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 22 14:51 EST 2020. Contains 332137 sequences. (Running on oeis4.)