

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
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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 11smooth: 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



